Preoperative selection of patients with severely impaired left ventricular function for coronary revascularization. Role of low-dose dobutamine echocardiography and exercise-redistribution-reinjection thallium SPECT

Lung and cardiac ultrasound for hemodynamic monitoring of patients with severe pre-eclampsia

OBJECTIVE

To evaluate lung and cardiac ultrasound for the assessment of fluid tolerance and fluid responsiveness before and after delivery in pregnant women with severe pre-eclampsia (PE).

METHODS

This was a prospective observational study of singleton pregnant women with severe PE and healthy term controls. Lung ultrasound echo comet score (ECS), which denotes the amount of extravascular lung water, was obtained using the 28-rib interspaces technique. The echocardiographic E/e' ratio, measured by pulsed-wave and tissue Doppler, was used as a marker of diastolic left ventricular function. Fluid responsiveness was assessed by measuring changes in stroke volume (SV) with passive leg raising (PLR). SV was calculated from the left ventricular flow velocity-time integral measured by pulsed-wave Doppler at baseline and after PLR. Change in SV ≥ 12% was considered to indicate fluid responsiveness. Measurements obtained 1 day before delivery and 1 and 4 days after delivery were compared in the two groups (PE vs controls).

RESULTS

We included 21 women with severe PE and 12 healthy controls. ECS and E/e' ratio were higher in women with PE than in controls, both before delivery (P = 0.002 and P = 0.02) and 1 day postdelivery (P = 0.02 and P = 0.03); however there was no difference at 4 days postdelivery (P = 0.63 and P = 0.90). The change in SV with PLR before (P = 0.26) and after (P = 0.71) delivery did not differ between groups. An increase in SV ≥ 12% was observed in three (14%) women with PE and four (33%) controls before delivery and in four (19%) women with PE and two (17%) controls 1 day after delivery.

CONCLUSIONS

Severe PE is associated with an increase in extravascular lung water, which could in part be caused by disturbed diastolic left ventricular function. Excess lung water can be identified by lung ultrasound assessment in women with severe PE before the appearance of clinical signs. Only a small proportion of these women are fluid responsive. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Lung Ultrasound Predicts Interstitial Syndrome and Hemodynamic Profile in Parturients with Severe Preeclampsia

Background:

The role of lung ultrasound has never been evaluated in parturients with severe preeclampsia. The authors’ first aim was to assess the ability of lung ultrasound to detect pulmonary edema in severe preeclampsia. The second aim was to highlight the relation between B-lines and increased left ventricular end-diastolic pressures.

Methods:

This prospective cohort study was conducted in a level-3 maternity during a 12-month period. Twenty parturients with severe preeclampsia were consecutively enrolled. Both lung and cardiac ultrasound examinations were performed before (n = 20) and after delivery (n = 20). Each parturient with severe preeclampsia was compared with a control healthy parturient. Pulmonary edema was determined using two scores: the B-pattern and the Echo Comet Score. Left ventricular end-diastolic pressures were assessed by transthoracic echocardiography.

Results:

Lung ultrasound detected interstitial edema in five parturients (25%) with severe preeclampsia. A B-pattern was associated to increased mitral valve early diastolic peak E (116 vs. 90 cm/s; P = 0.05) and to increased E/E’ ratio (9.9 vs. 6.6; P < 0.001). An Echo Comet Score of greater than 25 predicted an increase in filling pressures (E/E’ ratio >9.5) with a sensitivity and specificity of 1.00 (95% CI, 0.69 to 1.00) and 0.82 (95% CI, 0.66 to 0.92), respectively.

Conclusions:

In parturients with severe preeclampsia, lung ultrasound detects both pulmonary edema and increased left ventricular end-diastolic pressures. The finding of a B-pattern should restrict the use of fluid. However, these preliminary results are associations from a single sample. They need to be replicated in a larger, definitive study.

Outcome after redo coronary artery bypass grafting in patients with ischaemic cardiomyopathy and viable myocardium

BACKGROUND

Repeat coronary artery bypass grafting (redo-CABG) in patients with ischaemic cardiomyopathy is associated with high perioperative risk and worse long-term outcome compared with patients undergoing their first CABG.

OBJECTIVE

To assess whether patients with viable myocardium undergoing redo-CABG have a better outcome.

METHODS

18 patients with ischaemic cardiomyopathy underwent redo-CABG and 34 underwent their first CABG; all had substantial viability (> or =25% of the left ventricle) on dobutamine stress echocardiography (DSE). Left ventricular ejection fraction (LVEF) and heart failure symptoms were assessed before and 9-12 months after revascularisation. Cardiac event rate was assessed during the follow-up period (median 4 years, 25-75th centile 2.8-4.9 years).

RESULTS

The extent of viable myocardium on DSE was comparable in the two groups (11.3 (3.9) segments in patients who underwent redo-CABG v 12.8 (3.0) in patients who underwent their first CABG; p = NS). LVEF improved from 32% (9%) to 39% (12%); p = 0.01, in patients who underwent redo-CABG and from 30% (7%) to 36% (7%); p<0.01, in those who underwent their first CABG; New York Heart Association class improved from 2.5 (1.1) to 1.9 (0.8); p = 0.03, and from 2.7 (1.0) to 1.8 (0.70); p<0.01, respectively. In patients who underwent redo-CABG, the perioperative mortality was 0, post-surgery inotropic support was needed in 11% of the patients and mid-term (4-year) survival was 100%, with a total event rate of 28%. All these variables were not statistically different from patients who underwent their first CABG (p = 0.50, 0.90, 0.08 and 0.81, respectively).

CONCLUSION

Patients with ischaemic cardiomyopathy and substantial viability undergoing redo-CABG benefit from revascularisation in terms of improvement in LVEF, heart failure symptoms, angina and mid-term prognosis.

Benefits of coronary revascularisation in diabetic and non-diabetic patients with ischaemic cardiomyopathy: Role of myocardial viability

BACKGROUND

Diabetes mellitus in patients with coronary artery disease is associated with poor outcome. In this study, the relation between myocardial viability, diabetes, coronary revascularisation and outcome was evaluated.

METHODS

129 patients (31 diabetic, 98 non-diabetic) with ischaemic cardiomyopathy underwent dobutamine stress echocardiography to assess myocardial viability. Patients with >or=4 viable segments were defined as viable and patients with <4 viable segments as nonviable. Left ventricular ejection fraction (LVEF) was assessed before and 9-12 months post-revascularisation. At the same time-points, LV volumes were measured to evaluate LV remodelling. Finally, cardiac events were noted during 5-year follow-up.

RESULTS

The extent of viable myocardium was comparable between diabetic and non-diabetic patients. After revascularisation, LVEF increased >or=5% in 44% of diabetic and in 40% of non-diabetic patients. LVEF only improved in patients with viable myocardium. Ongoing LV remodelling occurred in 36% and 35% of diabetic and non-diabetic patients respectively, and was related to non-viability, whereas viability protected against ongoing LV remodelling, both in diabetic and non-diabetic patients. Viability was the only predictor of survival after revascularisation.

CONCLUSIONS

Diabetic, viable patients with ischaemic LV dysfunction exhibit improvement in LVEF post-revascularisation with prevention of ongoing LV remodelling, similar to non-diabetic patients. Myocardial viability was also the only predictor of long-term outcome.

Coronary Bypass Surgery for Patients with Chronic Poor Preoperative Left Ventricular Function (EF<30%): 5-year Follow-up

BACKGROUND

Optimal therapy for patients with coronary artery disease and chronic poor left ventricular function, given the absence of randomized trials, is unclear. Although coronary surgery has been performed in such patients for 25 years, it is perceived as high risk and unproven long-term benefit, especially if thallium scanning fails to demonstrate large areas of viability. We report the results of coronary surgery in these patients.

METHODS

Retrospective analysis by a standardized patient questionnaire, of 107 such consecutive patients offered coronary surgery.

RESULTS

Mean follow-up was 3.3 years (range, 0.5-5.5); average patient age was 64.4+/-1 years. Preoperative thallium scans were performed solely on 31 patients with none or mild angina, of which 10 (32%) demonstrated large areas of viable myocardium. Perioperative mortality was 1.9%. On multivariate analysis, factors predictive of increased perioperative death were recent myocardial infarction (p<0.001) and nonelective surgery (p<0.001). Kaplan-Meier 5-year survival and freedom from major adverse cardiac events were 72.3 and 82.3%, respectively. In 21 patients, with preoperative nil-to-mild angina and nil-to-small areas of myocardial viability, thallium scanning failed to predict a successful outcome.

CONCLUSION

Offering coronary surgery to these patients irrespective of thallium testing is safe and effective in the medium term. Early surgery is recommended.

The use of stress echocardiography for prognostication in coronary artery disease: an overview

PURPOSE OF REVIEW

Stress echocardiography has a high accuracy for the detection of coronary artery disease. Additionally, it provides clinically useful prognostic information, such as resting left ventricular function, myocardial viability, stress-induced ischemia, vascular extent of wall motion abnormalities, and changes in end-systolic volume and ejection fraction with stress.

RECENT DEVELOPMENTS

The timing, extent, and severity of the stress-induced wall motion abnormalities are important determinants of long-term prognosis. Previous studies have shown the efficacy of stress echocardiography in predicting long-term cardiac events in mixed patient groups and the value of this test in selected patient subsets.

SUMMARY

This review attempts to define the role of stress echocardiography for prognostication in coronary artery disease, pointing out the ability of this technique to identify low-risk and high-risk subsets among patients with known or suspected coronary artery disease and thus guide patient management decisions.

Relation of improvement in left ventricular ejection fraction versus improvement in heart failure symptoms after coronary revascularization in patients with ischemic cardiomyopathy

In the present study, the relation between improvement in the left ventricular ejection fraction (LVEF) and heart failure symptoms was evaluated in 100 patients with ischemic cardiomyopathy undergoing coronary revascularization. In patients with viable myocardium, the improvement in the LVEF after revascularization was accompanied by improvement in heart failure symptoms in most patients (80%); most viable patients (75%) without improvement in LVEF also showed an improvement in New York Heart Association functional class. Conversely, most nonviable patients failed to improve in LVEF or New York Heart Association class.

Detection of myocardial viability by dobutamine stress echocardiography: incremental value of diastolic wall thickness measurement

OBJECTIVE

To assess the diagnostic accuracy of baseline diastolic wall thickness (DWT) alone and as an adjunct to dobutamine stress echocardiography (DSE) for prediction of myocardial viability in patients with ischaemic left ventricular (LV) dysfunction, with the recovery of resting function after revascularisation as the yardstick.

PATIENTS

24 patients with ischaemic LV dysfunction (ejection fraction < 40%) scheduled for surgical revascularisation.

SETTING

Regional cardiothoracic centre.

METHODS

All patients underwent DSE before and resting echocardiography six months after revascularisation. DWT was measured in each of the 16 LV segments. A receiver operating characteristic (ROC) and a multi-ROC curve were generated to assess the ability of DWT alone and in combination with DSE to predict myocardial viability.

RESULTS

DWT > 0.6 cm provided a sensitivity of 80%, a specificity of 51%, and a negative predictive value of 80% for the prediction of viability in akinetic segments. DSE had an excellent specificity (92%) but a modest sensitivity (60%) in akinetic segments. A combination of improvement at DSE or DWT > 0.8 cm improved sensitivity (90% v 60%, p < 0.001) and negative predictive value (92% v 78%, p = 0.03) in akinetic segments compared with DSE alone. This was achieved with some loss in specificity (75% v 92%, p = 0.01) and positive predictive value (71% v 82%, p = 0.79).

CONCLUSIONS

DWT measurement may improve the sensitivity of DSE for the detection of myocardial viability. Akinetic segments with DWT > 0.8 cm have a good chance of recovery despite the absence of contractile reserve during DSE. Further testing may be required before excluding myocardial viability in these cases.

Long term prognostic value of myocardial viability and ischaemia during dobutamine stress echocardiography in patients with ischaemic cardiomyopathy undergoing coronary revascularisation

OBJECTIVE

To evaluate the relative merits of viability and ischaemia for prognosis after revascularisation.

METHODS

Low-high dose dobutamine stress echocardiography (DSE) was performed before revascularisation in 128 consecutive patients with ischaemic cardiomyopathy (mean (SD) left ventricular ejection fraction (LVEF) 31 (8)%). Viability (defined as contractile reserve (CR)) and ischaemia were assessed during low and high dose dobutamine infusion, respectively. Cardiac death was evaluated during a five year follow up. Clinical, angiographic, and echocardiographic data were analysed to identify predictors of events.

RESULTS

Univariable predictors of cardiac death were the presence of multivessel disease (hazard ratio (HR) 0.21, p < 0.001), baseline LVEF (HR 0.90, p < 0.0001), wall motion score index (WMSI) at rest (HR 4.02, p = 0.0006), low dose DSE (HR 7.01, p < 0.0001), peak dose DSE (HR 4.62, p < 0.0001), the extent of scar (HR 1.39, p < 0.0001), and the presence of CR in > or = 25% of dysfunctional segments (HR 0.34, p = 0.02). The best multivariable model to predict cardiac death included the presence of multivessel disease, WMSI at low dose DSE, and the presence of CR in > or = 25% of the severely dysfunctional segments (HR 9.62, p < 0.0001). Inclusion of ischaemia in the model did not provide additional predictive value.

CONCLUSION

The findings of the present study illustrate that in patients with ischaemic cardiomyopathy, the extent of viability (CR) is a strong predictor of long term prognosis after revascularisation. Ischaemia did not add significantly in predicting outcome.

Improvement of stress LVEF rather than rest LVEF after coronary revascularisation in patients with ischaemic cardiomyopathy and viable myocardium

OBJECTIVE

To evaluate prospectively the response of left ventricular ejection fraction (LVEF) to high dose dobutamine infusion in patients showing substantial viability, with and without improved resting LVEF after revascularisation.

METHODS

Before and 9-12 months after revascularisation, 50 patients with ischaemic cardiomyopathy (LVEF 32 (8)%) and substantial myocardial viability (> or = 4 viable segments) underwent radionuclide ventriculography and dobutamine stress echocardiography. Patients were divided into group 1, patients with, and group 2, patients without significant improvement in resting LVEF (> or = 5% by radionuclide ventriculography) after revascularisation. The response of LVEF during dobutamine stress echocardiography was compared in these two groups.

RESULTS

Groups 1 and 2 were comparable in baseline characteristics, resting LVEF, and number of viable segments (mean (SD) 7 (4) v 6 (2), not significant). After revascularisation, the LVEF response during dobutamine stress echocardiography improved significantly in both groups (group 1, 34 (10)% to 56 (8)%; group 2, 32 (10)% to 46 (11)%; both p < 0.001). Interestingly, although resting LVEF did not improve in group 2, peak stress LVEF after revascularisation did (p < 0.001). Group 1 patients had, however, a greater increase in peak stress LVEF (group 1, 22 (10)%; group 2, 13 (9)%; p < 0.01). New York Heart Association and Canadian Cardiovascular Society classes decreased in both groups.

CONCLUSIONS

Although patients with viable myocardium did not always have improved rest LVEF after revascularisation, peak stress LVEF improved. Assessment of improvement of resting function may not be the ideal end point to evaluate successful revascularisation.

Opposite patterns of left ventricular remodeling after coronary revascularization in patients with ischemic cardiomyopathy: role of myocardial viability

BACKGROUND

In patients with ischemic cardiomyopathy, left ventricular (LV) remodeling is an important prognostic indicator. The precise relation between viable myocardium, revascularization, and ongoing or reversed remodeling is unknown and was evaluated in the present study.

METHODS AND RESULTS

A total of 100 patients with ischemic cardiomyopathy underwent dobutamine stress echocardiography to assess myocardial viability and LV geometry (volumes and shape). At a mean of 10.2 months and 4.5 years after revascularization, resting echocardiography was repeated to evaluate LV remodeling. Long-term follow-up (mean 5+/-2 years) data were obtained. According to dobutamine stress echocardiography, 44 patients (44%) were defined as viable (> or =4 viable segments) and 56 as nonviable. After revascularization, 40 patients (43%) had ongoing LV remodeling and 53 (57%) did not (in 7 patients who died early after revascularization, postoperative echocardiographic evaluation was not available). On multivariable analysis, the number of viable segments was the only predictor of ongoing LV remodeling (OR 0.60, 95% CI 0.48 to 0.75; P<0.0001). The likelihood of LV remodeling decreased as the number of viable segments increased. During the follow-up, reverse remodeling was present in viable patients, whereas in nonviable patients, LV volumes significantly increased, which indicates ongoing LV remodeling. At follow-up, viable patients also showed a persistent improvement of heart failure symptoms and fewer cardiac events than nonviable patients (P<0.05).

CONCLUSIONS

In patients with ischemic cardiomyopathy, a substantial amount of viable myocardium prevents ongoing LV remodeling after revascularization and is associated with persistent improvement of symptoms and better outcome.

Comparison of long-term effect of coronary artery bypass grafting in patients with ischemic cardiomyopathy with viable versus nonviable left ventricular myocardium

In this study, 63% of patients with a substantial amount of viable myocardium showed an increased left ventricular ejection fraction (LVEF) 12 +/- 3 months after coronary artery bypass grafting. In 93% of these patients, increased LVEF persisted at 4.5 +/- 1 years of follow-up. Conversely, in nonviable patients, LVEF did not increase at 12 +/- 3 months or at follow-up of 4.5 +/- 1 years.

Does resting two-dimensional echocardiography identify patients with ischemic cardiomyopathy and low likelihood of functional recovery after coronary revascularization?

OBJECTIVE

To evaluate the potential of a simple and widely available technique as two-dimensional (2D) echocardiography to identify patients with ischemic cardiomyopathy and low likelihood of functional recovery after coronary revascularization.

METHODS

Two-dimensional echocardiography and radionuclide ventriculography (RNV) were performed before coronary revascularization in 94 patients with ischemic cardiomyopathy. Left ventricular ejection fraction (LVEF) was measured by RNV. Regional wall motion abnormalities, wall motion score index, end-diastolic wall thickness (EDWT), left ventricular (LV) volumes and LV sphericity index were assessed in the echocardiographic images. RNV was repeated 9-12 months after revascularization to assess LVEF change; an improvement >or=5% was considered clinically significant.

RESULTS

Nine hundred and ninety-nine segments were severely dysfunctional; 149 out of 999 (15%) had an EDWT <or=6 mm. A severe enlargement of the end-diastolic volume index (EDVI) (>or=100 ml/ml) and of the end-systolic volume index (>or=80 ml) was present in 32 (34%) and 21 (22%) patients, respectively. A spherical shape of the LV was observed in 35 (37%) patients. LVEF after revascularization increased in 30 out of 94 patients (32%) from 30+/-8% to 39+/-9% (P<0.0001). On multivariate analysis, the EDVI was the only predictor of no recovery in LVEF [odds ratio, 1.06, confidence interval (CI), 1.04-1.1, P<0.0001]. The cut-off value of EDVI >or=90 ml/ml accurately identified patients that virtually never recover. Post-operatively, LVEF increased in three out of 42 (7%, 95% CI 0-15%) patients with EDVI >or=90 ml/ml as compared to 27 out of 52 (52%) patients with EDVI<90 ml/ml (P<0.0001).

CONCLUSIONS

In patients with ischemic cardiomyopathy and severe LV enlargement, improvement of LVEF after revascularization is unlikely to occur. Conversely, in patients with relatively preserved LV size, a higher likelihood of functional recovery may be anticipated.

Ventricular function after coronary artery bypass grafting: Evaluation by magnetic resonance imaging and myocardial strain analysis

OBJECTIVE

Magnetic resonance imaging with radiofrequency tissue tagging permits quantitative assessment of regional systolic myocardial strain. We sought to investigate the utility of this imaging modality to quantitatively determine preoperative impairment and postoperative improvement in ventricular function in patients with ischemic heart disease.

METHODS

Magnetic resonance imaging with radiofrequency tissue tagging was performed on 6 patients (average age 60.2 +/- 13.7 years) with coronary artery disease and 32 control subjects with no known heart disease. Patients with coronary artery disease underwent imaging before and 3 months after coronary artery bypass grafting. The ventricle was divided into 6 segments within a midventricular plane. Regional 2-dimensional left ventricular circumferential strain was calculated from tagged magnetic resonance images throughout systole. Circumferential strain results were compared in patients before and after and 3 months after coronary artery bypass grafting and also in control subjects.

RESULTS

Before the operation circumferential strain identified 100% (10/10) of all regional wall motion abnormalities seen by preoperative ventriculography. Postoperatively, improvements were demonstrated in 56% (20/36) of the regions, and these improvements agreed with viability testing by single-photon emission computed tomography when available. Additionally, preoperative global circumferential strain for the ischemic group was significantly depressed relative to that in control subjects (0.11 +/- 0.05 vs 0.20 +/- 0.03, P <.001). Global circumferential strain correlated with ejection fraction by ventriculography (r = 0.84, P <.01) and improved after coronary artery bypass grafting (0.14 +/- 0.05 vs 0.11 +/- 0.05, P <.01).

CONCLUSIONS

Magnetic resonance imaging with radiofrequency tissue tagging permitted circumferential strain calculation. This technology quantitatively demonstrated improvements in left ventricular wall motion after coronary artery bypass grafting for both individual regions and the entire ventricle. This noninvasive method may prove useful in preoperative evaluation and postoperative serial assessment of left ventricular wall motion.

Myocardial revascularisation in patients with severe left ventricular dysfunction. Early and midterm results

AIMS

This retrospective study evaluates early and midterm results in patients with severe left ventricular dysfunction.

TECHNIQUE

Ninety-seven consecutive patients with coronary artery disease and ejection fraction of left ventricle (LVEF) less or equal to 25 % underwent elective coronary artery bypass graft procedure between September 1998 and December 2001. Mean age at operation was 66 (47-86) years. The main symptoms were angina class III-IV Canadian Cardiovascular Society (CCS) in 78 patients (80 %) and dyspnoea class III-IV New York Heart Association (NYHA) in 43 patients (44 %). The major indications for surgery were severe angina, dyspnoea in 90 patients (93 %). Cardiac index (CI), echocardiography (ECHO), planimetry, end-diastolic pressure of left ventricle (LVEDP), end-diastolic diameter of left ventricle (LVEDd) were used to access left ventricular function preoperatively. ECHO was also used to access left ventricular function postoperatively.

RESULTS

Early postoperative (30 days) mortality was 4.1 %. Complications had 25 patients (26 %) postoperatively. Two years survival was 95.7 %. Class III-IV CCS and/or NYHA had 17 patients (17.5 %) two years after surgery. LVEF (assessed by ECHO) improved from 23.1 % preoperatively to 36.0 % postoperatively (p < 0.05).

CONCLUSION

The study showed that elective myocardial revascularisation in patients with severe left ventricular dysfunction and signs of myocardial viability is not necessarily associated with high operative mortality. It can be performed safely with respectable midterm survival in concordance with left ventricular function improvement, symptom relief and quality of life improvement.

Comparison of functional recovery of mildly hypokinetic versus severely dysfunctional left ventricular segments after revascularization in patients with ischemic cardiomyopathy

Dysfunctional left ventricular (LV) segments showing contractile reserve during dobutamine stress echocardiography (DSE) are considered viable myocardium; functional recovery is expected after revascularization. Many segments, however, particularly mildly hypokinetic segments, do not recover. The reason for this failure is unknown. Two-dimensional echocardiography at rest and low-high-dose DSE were performed before revascularization in 114 consecutive patients with ischemic cardiomyopathy. Two-dimensional echocardiography at rest was repeated after 9 to 12 months. Segmental function was scored by a 5-point grading score. Functional recovery after revascularization was assessed in mildly hypokinetic (score 2, group I) and severely dysfunctional segments (score 3 to 5, group II). For each segment, functional recovery was defined as an improvement in functional score of > or =1 grade compared with the baseline score at rest. During low-dose DSE (up to 10 microg/kg/min), 183 group I segments (68%) and 438 group II (39%) segments had contractile reserve (p <0.0001). However, functional recovery was observed less frequently in group I segments (41%) than in group II segments (55%) with contractile reserve (p <0.005). During high-dose DSE (up to 40 microg/kg/min), in the group I segments with contractile reserve at the low dose, the sustained improvement pattern (indicating subendocardial scar) was prevalent (73%). After revascularization, 73% of segments with sustained improvement did not recover. Conversely, the biphasic response (indicating ischemically jeopardized myocardium) was observed only in 27% of group I segments. Functional recovery occurred in 39 of these segments (78%) (p <0.001 vs sustained improvement). Hence, mildly hypokinetic segments probably indicate the presence of subendocardial scars, and may explain the failure in functional recovery after revascularization.

Additive value of low-dose dobutamine to technetium-99m sestamibi-gated single-photon emission computed tomography for prediction of wall motion improvement in patients undergoing coronary artery bypass graft

BACKGROUND

The two most useful methods for myocardial viability assessment are perfusion imaging and dobutamine echocardiography.

HYPOTHESIS

The present study investigated the additive value of a new method, dobutamine technetium 99m (99mTc)-sestamibi-gated single-photon emission computed tomography (SPECT), which combines these two modalities, to the prediction of wall motion improvement after revascularization.

METHODS

Fifty-five consecutive patients with ischemic cardiomyopathy, who were referred for viability evaluation, underwent resting and dobutamine (dose, 5-10 microkg/kg/min) gated SPECT with 99mTc-sestamibi. Of these patients, 36 underwent coronary artery bypass graft (CABG) within 1 month of the study and 32 had repeat resting gated SPECT within 1 year. Global and regional wall motion, wall thickness, and perfusion were simultaneously analyzed at rest and after dobutamine using the 20-segment model; the sestamibi uptake and wall motion response to dobutamine of each segment were rated quantitatively. Based on these findings, the segments were categorized as normal, viable, or nonviable. The predictive values for wall motion improvement were assessed by perfusion, using cutoffs of 50 and 60% of sestamibi uptake, and thereafter by the addition of dobutamine response in the segments that were rated nonviable.

RESULTS

Of the 1,080 myocardial segments studied, 906 (84%) had abnormal wall motion and were analyzed for viability. Concordance between perfusion and wall motion response to dobutamine was 60% with the 50% cutoff of sestamibi uptake, and increased to 65% with the 60% sestamibi cutoff (p < 0.04). The respective predictive values of wall motion improvement using the 50 and 60% cutoff points were as follows: sensitivity 93 and 70%, respectively, (p < 0.01); specificity 59 and 86% (p < 0.001), respectively; accuracy 77% for both. The addition of the wall motion response to dobutamine to the assessment of the nonviable segments by perfusion (60% cutoff) increased the sensitivity from 70 to 85% (p = 0.001) and the negative predictive value from 70 to 81% (p = 0.009); the positive predictive value remained high (86 vs. 82%). No additive value of wall motion response to dobutamine was demonstrated for nonviable segments by perfusion with a 50% cutoff.

CONCLUSION

Dobutamine sestamibi-gated SPECT is a feasible method for the analysis of myocardial perfusion, function, and contractile reserve of individual myocardial segments in patients with ischemic cardiomyopathy. Viability assessment based on a threshold of 60% uptake of sestamibi, with the addition of the wall motion response to dobutamine in the nonviable segments, seems to yield better predictive values for wall motion improvement after CABG.

Coronary revascularization in ischemic cardiomyopathy

This article first discusses coronary artery disease, including left-ventricular dysfunction, hibernating myocardium, the relationship between stunning, hibernation, and heart failure, and molecular mechanisms underlying myocardial hibernation. Left ventricular function and the prognosis and pathophysiology of left-ventricular dysfunction are then examined. Selection of patients for revascularization is discussed, to include which coronary patients should be investigated for myocardial viability, and other surgical considerations are outlined. The outcome following revascularization in the heart failure patient, the results of revascularization, and the time course of functional recovery after coronary artery bypass graft are also covered.

Relationship between dobutamine response of dyssynergic myocardium and angiographically documented blood supply

OBJECTIVE

Because hibernation is considered a down-regulation of contractile function in response to reduced regional myocardial perfusion, hibernating myocardium is expected to be supplied by a critically stenosed or even occluded coronary artery. Thus, high-dose dobutamine has been postulated to cause ischemia and reworsening of myocardial function (biphasic response), whereas myocardium that demonstrates sustained improvement with high-dose dobutamine should not be supplied by a significantly stenosed vessel. This study evaluates the type of dobutamine response-biphasic versus sustained improvement-of dyssynergic myocardium in relation to its angiographically documented blood supply.

METHODS

In 38 patients (5 women; mean age 60 +/- 9 years) with chronic coronary artery disease and impaired left ventricular ejection fraction (</=35%), dobutamine echocardiography and quantitative coronary angiography were performed within 4 weeks. Wall-motion response of dyssynergic myocardium to dobutamine, classified as no improvement, biphasic response, or sustained improvement, was compared with the angiographically documented blood supply (presence of coronary stenosis in the corresponding artery, collaterals, and stenoses of the collateral supplying artery) in a segment-by-segment analysis.

RESULTS

Of the 465 segments with abnormal wall motion at rest, 201 (47%) showed improvement during dobutamine infusion at low dose. Of these, 145 (72%) were supplied by significantly stenosed epicardial vessels. Only 27 (19%) of these 145 segments showed a biphasic response whereas in the remaining 118 segments wall-motion improvement persisted during high-dose dobutamine infusion. Although mean stenosis severity in the supplying vessel was significantly greater for segments presenting with biphasic response as compared with sustained improvement (95 +/- 7% and 86 +/- 12% luminal diameter reduction, respectively; P <.0001), 69% of segments with sustained improvement were supplied by a critically stenosed artery. Only 7 of 27 segments with biphasic response and 22 of 118 segments with sustained improvement had visible collaterals supplied by a vessel without significant stenosis. The percentage of segments viable by thallium-single photon emission computed tomography imaging was similar for those with sustained and biphasic response (96% and 83%, respectively).

CONCLUSIONS

In this group of patients with coronary artery disease and impaired left ventricular function, the great majority of dyssynergic segments that exhibited a sustained, rather than biphasic, dobutamine response were supplied by a critically stenosed artery. Furthermore, the percentage of segments viable by thallium-single photon emission computed tomography did not appear to be different for segments with sustained improvement and those with biphasic response. These findings challenge the hypothesis that biphasic response is the best criterion to identify viable myocardium.

Individual prediction of functional recovery after coronary revascularization in patients with ischemic cardiomyopathy: the scar-to-biphasic model

Currently, the prediction of improvement of left ventricular (LV) ejection fraction (EF) after revascularization in patients with ischemic cardiomyopathy relies only on viable myocardium extent, whereas both the amount of viable and scar tissue may be important. A model was developed, based on the amount of viable and nonviable myocardium, to predict functional recovery. Viable and scarred myocardium was defined by dobutamine stress echocardiography (DSE) in 108 consecutive patients. LVEF before and 9 to 12 months after revascularization was assessed by radionuclide ventriculography; an improvement of > or =5% was considered significant. In the 1,089 dysfunctional segments (63%), DSE elicited biphasic response in 216 segments (20%), sustained improvement in 205 (19%), worsening in 43 (4%), and no change in 625 (57%). LVEF improved in 39 patients (36%). Only the numbers of biphasic and scar segments were predictors of improvement or no improvement of LVEF (odds ratio 1.5, 95% confidence interval 1.2 to 1.7, p <0.0001 for biphasic segments; odds ratio 0.8, 95% confidence interval 0.7 to 0.9, p <0.0005 for scarred segments). The sustained improvement and worsening pattern were not predictive of improvement or no improvement. A regression function, based on the number of scar and biphasic segments, showed that the likelihood of recovery was 85% in patients with extensive biphasic tissue and no scars and 11% in patients with extensive scars and no biphasic myocardium. Patients with a mixture of scar and biphasic tissue had an intermediate likelihood of improvement (50%). In patients with ischemic cardiomyopathy and a mixture of viable and nonviable tissue, both numbers of viable and nonviable segments should be considered to accurately predict functional recovery after revascularization.

Is there a long-term predictive value of intraoperative low-dose dobutamine echocardiography in patients who have coronary artery bypass graft surgery with cardiopulmonary bypass?

In patients with coronary artery disease, chronic regional left ventricular systolic dysfunction at rest may be caused by hibernating or by infarcted myocardium. Intraoperative low-dose dobutamine (LDD) echocardiography reliably predicts the immediate recovery of regional myocardial function after coronary artery bypass graft (CABG) surgery. We sought to determine whether intraoperative LDD echocardiography would also predict recovery of regional function after 1 yr. Twenty-five patients with coronary artery disease who underwent CABG surgery with intraoperative LDD echocardiography were evaluated 1 yr later with a follow-up transthoracic echocardiogram. The covariates of left ventricular ejection fraction, old myocardial infarction, and diabetes mellitus were considered in an analysis of regional wall motion (RWM). A 16-segment model and a 1-5-point scoring system were used to evaluate 350 myocardial segments. Multiple logistic regression analysis was performed to determine whether response to intraoperative LDD echocardiography (5 microg. kg(-1). min(-1)) predicted changes in regional function at 1 yr. A segment was defined as stunned if the RWM score obtained during LDD infusion deteriorated after cardiopulmonary bypass but recovered in the 1-yr follow-up echocardiogram. A response to intraoperative LDD predicted changes in regional function at 1 yr. The overall odds of improvement in regional function were 2.22 times greater (95% confidence interval = 1.29, 3.82; P = 0.0039) with a positive response to intraoperative LDD. The positive predictive value of intraoperative LDD echocardiography for improvement in myocardial function was 0.81 and the negative predictive value was 0.34. The predictive values did not vary with the examined covariates. Of segments with unexpected deterioration of RWM immediately after cardiopulmonary bypass, 87% recovered at the time of the 1-yr follow-up echocardiogram. Contractile reserve demonstrated by intraoperative LDD echocardiography predicts regional function at 1 yr; however, the test cannot predict which segment will not recover. Most of unexpected regional ventricular systolic dysfunction immediately after CABG surgery can be attributed to myocardial stunning.

IMPLICATIONS

In patients undergoing coronary artery bypass graft surgery, intraoperative low-dose dobutamine echocardiography has only limited value for the prediction of regional myocardial function at 1 yr. Small-dose dobutamine echocardiography predicts regional myocardial function at 1 yr when baseline regional wall motion abnormalities improve with dobutamine; however, the test cannot be used to predict which segment will not recover at 1 yr.

[Comparison of dobutamine echocardiography and rest-redistribution 201-thallium SPECT in the assessment of myocardial viability taking PET as gold standard]

BACKGROUND AND AIM

To compare Tl-201 SPECT and dobutamine stress echocardiography for the detection of myocardial viability in patients with severe left ventricular dysfunction using metabolic imaging by positron emission tomography as the standard reference.

MATERIAL AND METHODS

We studied 25 consecutive patients with severe coronary artery disease and left ventricular dysfunction that underwent two different diagnostic modalities for evaluating myocardial viability: stress echocardiography with incremental doses of dobutamine from 5 up to 40 g/kg/min in 3 min stages, and 201 Tl SPECT using a rest-redistribution protocol with delayed images obtained at 4 hours. Fluorodeoxyglucose uptake by PET was used as the gold standard. Viability criteria were as follows, for 201Tl SPECT imaging: normal uptake at rest and presence of redistribution in the delayed images, for dobutamine stress echocardiography: sustained improvement and biphasic response.

RESULTS

Sensitivity of thallium redistribution was 46%, for normal uptake, plus redistribution 82%, 34% for dobutamine biphasic response and 58% for sustained improvement plus biphasic response. Specificity of biphasic response was 82% and that of redistribution 67%. Stepwise logistic regression indicated that biphasic wall motion response during dobutamine stress echocardiography (2.01 CI 95%; 1.10 to 3.99) and the presence of redistribution plus normal uptake at rest with thallium imaging (2.68 CI 95%; 1.42 to 5.13) were the best predictors of viability. These results were the same when both techniques were analyzed together.

CONCLUSIONS

Biphasic wall motion response during dobutamine stress echocardiography and the normal uptake plus presence of redistribution with thallium imaging were the best pre

Myocardial revascularization in patients with severe ischemic left ventricular dysfunction. Long term follow-up in 141 patients

OBJECTIVES

The present study evaluates our experience with coronary bypass grafting in patients with EF < or =25%. Myocardial revascularization in this setting remains controversial because of concerns over operative mortality and morbidity and lack of functional and survival benefit.

MATERIALS AND METHODS

One hundred and forty-one patients with coronary artery disease and left ventricular ejection fraction < or =25% underwent coronary artery bypass graft between January 1988 and December 1998. Mean age at operation was 63.3 years and 81.4% were male. The major indication for surgery was angina (114 patients, 80.8%). Ejection fraction (EF), left ventricular end diastolic pressure (LVEDP) and cardiac index (CI) were used to assess left ventricular function. The number of graft was 2.7+/-1.6/patient. Internal mammary artery was used in 119 patients (84.3%). Intra aortic balloon pump was placed preoperatively in 25 patients (17.7%). Five operative risk factors were associated with a higher mortality: emergency, female sex, LVEDP, CI and NYHA class IV.

RESULTS

The operative mortality was 7% (10 patients). Left ventricular ejection fraction (assessed post operatively in 83 patients) improved from 22.2% preoperatively to 33.5% post operatively (P<0.001), mean end diastolic volume index fell from 98 to 83 ml/m(2) following surgery. Survival at 2, 5 and 7 years was respectively 84+/-3%, 70+/-4% and 50+/-5%. Two variables were associated with increased long term survival: congestive heart failure (NYHA class lower than IV (P=0.035) and cardiomegaly (P=0.04)

CONCLUSION

In patients with left ventricular dysfunction, myocardial revascularization can be performed relatively safely with good medium term survival and improvement in quality of life and in left ventricular function. Coronary artery bypass graft may be offered to patients with impaired ventricular function, but careful patient selection and management when considering these patients for operation should assess potentially reversible dysfunction.

Relation between Gd-DTPA contrast enhancement and regional inotropic response in the periphery and center of myocardial infarction

BACKGROUND

Gd-DTPA contrast-enhanced (CE) MRI identifies patterns of early hypoenhancement and delayed hyperenhancement in acute myocardial infarction, but their clinical significance for the prediction of myocardial viability remains controversial. Therefore, we closely examined the relationship between these CE patterns and regional inotropic response to low-dose dobutamine infusion at a regional level.

METHODS AND RESULTS

Thirteen dogs underwent CE and tagged MRI at rest and during 5 microg. kg(-1). min(-1) dobutamine 48 hours after MI. CE patterns and 3D regional strains were measured in 96 segments per animal. Segments were categorized as being normofunctional (n=828) if resting circumferential shortening was within the range of remote myocardium, or dysfunctional (n=420) if not. Inotropic response in resting dysfunctional segments was assessed according to CE patterns. Significant improvement of radial thickening (from +12+/-1% [mean+/-SEM] to +22+/-2%, P<0.05) and circumferential shortening (from +1+/-1% to -5+/-1%, P<0.05) strains occurred in dysfunctional myocardium with normal CE pattern but not in myocardium with early hypoenhancement. Delayed hyperenhanced myocardium displayed a more complex behavior. Circumferential stretching improved in the peripheral regions (from +4+/-1% to -2+/-2%, P<0.05), where the infarct was nontransmural (38+/-3% transmurality), but not in centrally hyperenhanced regions (from +4+/-1% to +1+/-1% P=NS), where the infarct was 66+/-3% transmural.

CONCLUSIONS

Inotropic reserve was confined to dysfunctional myocardium with normal contrast enhancement but not to myocardium with early hypoenhancement. Inotropic response in delayed hyperenhanced myocardium is influenced by transmurality of necrosis. These observations support the use of CE MRI for the clinical detection of myocardial viability.

[Thallium-201 scintigraphy and dobutamine echocardiography in the assessment of myocardial viability]

BACKGROUND

The possibility of differentiating viable from non-viable tissue among patients with severe coronary artery disease and severe left ventricular impairment entails relevant clinical and therapeutic implications since it may influence the indication of patient revascularization. To evaluate the presence of myocardial viability two techniques are available in the clinical setting: echocardiography with intravenous infusion of dobutamine and scintigraphy with myocardial perfusion with thalliem-201 by means of single-photon emission tomography.

OBJECTIVE

To compare prospectively the value of these techniques for detecting viable myocardium.

MATERIAL AND METHODS

Thirty-five patients with severe coronary disease and severe left ventricular dysfunction were included in the study. All patients underwent an echocardiogram using incremental doses of dobutamine, from 5 up to 40 micrograms/kg/min in three-minute periods. For thallium-201 scintigraphy the rest redistribution protocol with delayed images at 4 hours was used. The criteria for detecting viability were: a) for thallium-201, the presence of redistribution in delayed images and normal uptake at rest, and b) for dobutamine echocardiography, a sustained improvement in regional motion, biphasic response, and worsening.

RESULTS

By considering the segmental improvement post-revascularization as "gold standard" of viability, the statistically significant variables in a logistic regression model and, therefore, predictors of segmental functional recovery were the biphasic response and the sustained response for dobutamine echocardiography and normal uptake at rest and redistribution in the delayed images for thallium-201. Taken together, the result was significant for the biphasic response of dobutamine echocardiography.

CONCLUSIONS

The biphasic response with dobutamine echocardiography is the echocardiographic pattern that best predicts the functional recovery of the ischemic myocardium. A normal uptake and redistribution at four hours is the only scintigraphic pattern that can predict functional improvement. Of both patterns, the biphasic response is the best predictor of the functional recovery of the dysfunctional myocardium.

Usefulness of the ejection fraction response to dobutamine infusion in predicting functional recovery after coronary artery bypass grafting in patients with left ventricular dysfunction

Quantification of dysfunctional but viable myocardium has high prognostic value for improvement of left ventricular (LV) function after coronary artery bypass grafting (CABG). Dobutamine stress echocardiography (DSE) can assess viable myocardium by segmental wall motion changes during stress. However, analysis of wall motion is subjective with only moderate interinstitutional agreement (70%) and frequently overestimates functional improvement after CABG. In contrast, calculation of ejection fraction (EF) is less subjective and allows a more precise quantification of global contractile reserve. The aim of the study was to compare the prognostic value of EF response and segmental wall motion changes during DSE for the prediction of LV functional recovery after CABG. Forty patients underwent DSE before CABG. EF responses were assessed at rest, low-dose dobutamine, and at peak stress using the biplane disk method. Wall motion was scored using a 16-segment 5-point model. Resting radionuclide ventriculography (RNV-LVEF), performed before and 8 +/- 2 months after CABG, was used as an independent reference. Five patients were excluded because of perioperative infarction or poor echo images. In 11 of 35 patients, RNV-LVEF recovered >5%. Improvement in EF during dobutamine infusion predicted RNV-LVEF recovery after CABG significantly better than segmental wall motion changes (72% vs 53%, p = 0.03). A biphasic EF response (i.e., improvement in > or =10% at low dose and subsequent worsening at peak stress) had the highest predictive value (80%) for late functional recovery. In conclusion, EF response to dobutamine infusion was superior to segmental wall motion changes in predicting RNV-LVEF recovery after CABG.

Myocardial viability

This article reviews various means to assess myocardial viability by imaging, and provides recommendations for current clinical practice. This article also discusses future directions in assessing myocardial viability.

Assessment of myocardial viability by dobutamine echocardiography, positron emission tomography and thallium-201 SPECT: correlation with histopathology in explanted hearts

OBJECTIVES

We examined the relationship among viability assessment by dobutamine echocardiography (DE), positron emission tomography (PET) and thallium-201 single-photon emission computed tomography (TI-SPECT) to the degree of fibrosis.

BACKGROUND

DE, PET and TI-SPECT have been shown to be sensitive in identifying viability of asynergic myocardium. However, PET and TI-SPECT indicated viability in a significant percentage of segments without dobutamine response or functional improvement after revascularization.

METHODS

Twelve patients with coronary artery disease and severely reduced left ventricular function (EF 14.5+/-5.2%) were studied with DE prior to cardiac transplantation: 5 had additional PET and 7 had TI-SPECT studies. Results of the three techniques were compared to histologic findings of the explanted hearts.

RESULTS

Segments with >75% viable myocytes by histology were determined to be viable in 78%, 89% and 87% by DE, PET and TI-SPECT; those with 50-75% viable myocytes in 71%, 50% and 87%, respectively. Segments with 25-50% viable myocytes showed response to dobutamine in only 15%, but were viable in 60% by PET and 82% by TI-SPECT. Segments with <25% viable myocytes responded to dobutamine in 19%; however, PET and TI-SPECT demonstrated viability in 33% and 38%, respectively. Discrepant segments without dobutamine response but viability by PET and SPECT had significantly more viable myocytes by pathology than did those classified in agreement to be nonviable but had significantly less viable myocytes than those classified in agreement to be viable (p < .001).

CONCLUSIONS

These findings suggest that contractile reserve as evidenced by a positive dobutamine response requires at least 50% viable myocytes in a given segment whereas scintigraphic methods also identify segments with less viable myocytes. Thus, the methods may provide complementary information: Nuclear techniques appear to be highly sensitive for the detection of myocardial viability, and negative tests make it highly unlikely that a significant number of viable myocytes are present in a given segment. Conversely, dobutamine echo may be particularly useful for predicting recovery of systolic function after revascularization.

Relation of myocardial perfusion at rest and during pharmacologic stress to the PET patterns of tissue viability in patients with severe left ventricular dysfunction

BACKGROUND

Stress perfusion imaging can assess effectively the amount of jeopardized myocardium, but its use for identifying underperfused but viable myocardium has yielded variable results. We evaluated the relation between measurements of myocardial perfusion at rest and during pharmacologic stress and the patterns of tissue viability as determined by positron emission tomographic (PET) imaging.

METHODS AND RESULTS

We studied 33 patients with coronary artery disease and left ventricular (LV) dysfunction (LV ejection fraction, 30%+/-8%). PET imaging was used to evaluate regional myocardial perfusion at rest and during pharmacologic stress with [13N]-ammonia as a flow tracer, and to delineate patterns of tissue viability (i.e., perfusion-metabolism mismatch or match) using [18F]-deoxyglucose (FDG). We analyzed 429 myocardial regions, of which 229 were dysfunctional at rest. Of these, 30 had normal perfusion and 199 were hypoperfused. A severe resting defect (deficit >40% below normal) predicted lack of significant tissue viability; 31 of 35 regions (89%) had a PET match pattern denoting transmural fibrosis. Although regions with mild or moderate resting defects (deficit <40% below normal) showed evidence of metabolic activity, perfusion measurements alone failed to identify regions with PET mismatch (reflecting hibernating myocardium). Reversible stress defects were observed with slightly higher frequency in regions with a PET mismatch (10 of 37) than in those with a PET match (36 of 162) pattern of viability. A reversible stress defect was a specific (78%) marker, but was a relatively insensitive marker (27%) of viable myocardium as defined by the PET mismatch pattern.

CONCLUSIONS

In patients with LV dysfunction, the severity of regional contractile abnormalities correlates with the severity of flow deficit at rest. Severe reductions in resting blood flow in these dysfunctional regions identify predominantly nonviable myocardium that is unlikely to have improved function after revascularization. Although dysfunctional myocardium with mild to moderate flow reductions contains variable amounts of viable tissue (as assessed by FDG uptake), flow measurements alone do not distinguish between regions with PET mismatch (potentially reversible dysfunction) and PET match (irreversible dysfunction). The presence of an irreversible defect on stress imaging is a relatively specific (78%) marker of PET match, whereas a reversible stress defect is a rather insensitive (27%) marker of viability, as defined by the PET mismatch pattern.

Does the extended use of arterial grafts compromise the myocardial recovery after coronary artery bypass grafting in left ventricular dysfunction?

OBJECTIVE

To assess the prognostic factors of myocardial recovery expected after coronary bypass surgery and the impact of surgical technique used, a prospective non-randomized study including a 1-year postoperative evaluation of left ventricular function was performed in patients with left ventricular dysfunction (left ventricular ejection fraction (LVEF) < 0.40).

METHODS

From 1993 to 1996, 110 patients (mean age 61+/-11 years) were included in the study. The mean LVEF was 31+/-6%. All patients had preoperative radionuclide investigations based on the combination of stress/reinjection thallium single photon emission computed tomography (SPECT) and planar evaluation of LVEF; 88% of patients had reversible ischemic thallium defects. Two surgical technique were used: 53 patients received the left internal mammary artery with associated sequential vein graft, and 57 patients received only arterial grafts, internal mammary and gastroepiploic arteries. The mean number of distal anastomoses was 3.2+/-0.8 and 54% of patients had complete revascularization. At 1 year, all survivors had clinical evaluation and the same radionuclide investigations.

RESULTS

The early mortality was 2.7%. At 1 year, 100 patients were surviving; on average, NYHA class decreased 1.9+/-0.8 to 1.4+/-0.6 (P < 0.01) and CCS class from 2.8+/-0.6 to 1+/-0.3 (P < 0.01). The mean LVEF increase from 31+/-9 to 34+/-10% (P < 0.01) and the mean LV end-diastolic volume decreased from 317+/-112 to 285+/-108 ml (n.s.). The postoperative improvement in LV function was higher in patients in NYHA class 3 or 4 before surgery (P < 0.05), when associated sequential vein graft had been used (P < 0.01), and in patients with low preoperative LVEF (P < 0.01). The postoperative LVEF improvement observed was significantly correlated with the improvement in left ventricular end-diastolic (LVED) volume and the improvement in redistribution/reinjection thallium uptake. Multivariate analysis showed that the surgical technique used and the preoperative LVEF were independent prognostic factors of the postoperative myocardial function recovery, with a significant positive impact of the vein use.

CONCLUSION

This study confirms the excellent clinical results of coronary artery bypass grafting (CABG) in patients with coronary artery disease and LV dysfunction; improvement in LV function can be documented objectively and is correlated with reperfusion of hibernating myocardium. However, the extended use of arterial grafts does not allow to achieve the significant myocardial recovery observed with the use of one internal mammary artery (IMA) and associated sequential vein graft; it seems to be related to the preoperative selection of patients, but a direct negative impact of arterial grafts was documented and leads to be cautious in patients with severe LV dysfunction.

Myocardial viability during dobutamine echocardiography predicts survival in patients with coronary artery disease and severe left ventricular systolic dysfunction

OBJECTIVES

The purpose of this study was to assess whether the presence or absence of myocardial viability during dobutamine echocardiography (DE) predicts survival in patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction.

BACKGROUND

In patients with CAD, the presence of myocardial viability during DE identifies viable myocardium and predicts recovery of LV systolic function after revascularization. However, there is little data on the relation between myocardial viability and clinical outcome in patients with CAD and severe LV dysfunction.

METHODS

We studied 318 patients with CAD and a LV ejection fraction (EF) < or =35% who underwent DE and were followed for 18+/-10 months. Patients were classified into four groups. Group I (n=85) consisted of patients who had evidence of myocardial viability and subsequently underwent revascularization. Group II (n=119) consisted of patients with myocardial viability who did not undergo revascularization. Group III (n=30) consisted of patients who did not have myocardial viability and underwent revascularization. Finally, group IV (n=84) patients lacked myocardial viability and did not undergo revascularization.

RESULTS

The four groups had similar baseline characteristics and rest LVEF. During follow-up there were 51 deaths (16%). The mortality rate was 6% in group I, 20% in group II, 17% in group III and 20% in group TV (p=0.01, group I vs. other groups).

CONCLUSIONS

In patients with CAD and severe LV dysfunction who demonstrated myocardial viability during DE, revascularization improved survival compared with medical therapy.

Prognostic value of detection of myocardial viability using low-dose dobutamine echocardiography in infarcted patients

Revascularization can improve ventricular function in patients with viable myocardium, but whether and how the presence of viable myocardium affects prognosis of infarcted patients is still far from clear. Thus, 202 patients (173 men, 59 +/- 9 years old) with a previous or recent myocardial infarction (MI) and regional asynergies underwent low-dose dobutamine echocardiography (5-15 microg/kg per min) to assess myocardial viability and were followed for a period of 16 +/- 11 months after revascularization (89 patients) or medical therapy (113 patients). Four groups of patients were defined: (1) patients with viability, revascularized (n = 64); (2) patients with viability, treated medically (n = 52); (3) patients without viability, revascularized (n = 25); and (4) patients without viability, treated medically (n = 61). Of these patients, 45 (23%) patients suffered 57 cardiac events: 18 cardiac deaths (9%), 7 MIs, 12 unstable angina, 9 heart failures, and 11 new revascularization procedures. Patients with viability, revascularized, experienced a slightly lower event rate (22%) compared with patients with viability, treated medically, patients without viability, treated medically and patients without viability, revascularized (29%, 31%, and 36%, respectively; p = not significant [NS]). The frequency of events was then evaluated in those 108 patients with an ejection fraction < or =33%, in whom 14 cardiac deaths occurred: the incidence of cardiac death was slightly lower in patients with viability, revascularized (3/37, 8%) than in the patients with viability, treated medically (4/26, 15%), patients without viability, revascularized (2/11, 18%), or patients without viability, treated medically (5/34, 15%) (p = NS). Nonfatal cardiac events were significantly fewer (p <0.05) in patients with viability, revascularized (8%) and in patients without viability, treated medically (6%) than in patients with viability, treated medically and patients without viability, revascularized (27%). In infarcted patients with severe left ventricular dysfunction, the presence of viable myocardium, if left unrevascularized, leads to further events. On the contrary, in the absence of myocardial viability, revascularization could lead to a worse prognosis than medical therapy.

Correlation of myocardial histologic changes in hibernating myocardium with dobutamine stress echocardiographic findings

OBJECTIVE

The objective of this study was to correlate histologic changes in hibernating myocardium with dobutamine stress echocardiography (DSE).

METHODS

Patients (n = 8) with anterior regional wall motion abnormalities in the seven echocardiographic segments representing the territory supplied by a significantly stenosed left anterior descending coronary artery had preoperative DSE performed (yielding 56 segments for analysis). Two transmural biopsy specimens were taken from the anterior wall of the left ventricle during coronary artery bypass grafting.

RESULTS

Morphometric histologic analysis of biopsy specimens showed significantly less fibrosis in segments demonstrating inotropic reserve (p < 0.05) and significantly less fibrosis in segments demonstrating improvement in wall motion on echocardiography 3 months after revascularization (p < 0.05). DSE had a sensitivity of 100% and a specificity of 62% for detection of hibernating myocardial segments. Percent fibrosis was inversely correlated with percent nucleated cells (r = 0.66, p < 0.01) and directly correlated with cytoplasmic clearance (r = 0.76, p < 0.01).

CONCLUSION

Inotropic response during DSE correlates with histologic evidence of hibernating myocardium.

Biphasic response to dobutamine predicts improvement of global left ventricular function after surgical revascularization in patients with stable coronary artery disease: implications of time course of recovery on diagnostic accuracy

OBJECTIVES

This study sought to evaluate the time course of improvement of left ventricular (LV) dysfunction in stable patients and its implications on the accuracy of dobutamine echocardiography for predicting improvement after surgical revascularization.

BACKGROUND

Little is known about the optimal timing for evaluation of postrevascularization recovery of the contractile function of viable myocardium.

METHODS

Sixty-one patients with chronic ischemic LV dysfunction scheduled for elective surgical revascularization were prospectively selected. They underwent dobutamine echocardiography (5 to 40 microg/kg body weight per min) and radionuclide ventriculography both preoperatively and at 3-month follow-up. At 14 months, another evaluation of LV function was obtained. To analyze echocardiograms, a 16-segment model and a five-point scoring system were used. Dyssynergic segments were considered likely to recover in the presence of a biphasic contractile response to dobutamine. Improvement of global function was defined as a > or =5% increase in LV ejection fraction (LVEF).

RESULTS

Of the 61 patients, LVEF improved in 12 at 3 months and in 19 at late follow-up (from 32+/-8% to 42+/-9%, p < 0.0001). The frequency and time course of improvement of LVEF were similar in patients with mild and severe LV dysfunction. A biphasic response, identified in 186 of the 537 dyssynergic segments, was predictive of recovery in 63% at 3 months and in 75% at late follow-up. The positive predictive value was best in the most severe dyssynergic segments (90% vs. 67%). Other responses were highly predictive for nonrecovery (92%). The sensitivity and specificity for improvement of global function on a patient basis (> or =4 biphasic segments) were 89% and 81%, respectively, at late follow-up.

CONCLUSIONS

Serial postoperative follow-up studies demonstrate incomplete recovery of contractile function at 3 months. The diagnostic accuracy of dobutamine echocardiography for predicting recovery is dependent on three factors: the combining of low and high dobutamine dosages, the severity of regional dyssynergy and the timing of evaluation.

Evaluation of hibernating myocardium in patients with ischemic heart disease

Patients with ischemic heart disease and significant left ventricular dysfunction are often difficult to manage medically. Revascularization procedures may improve left ventricular function and prognosis in this population if hypocontractile yet viable myocardium (hibernating myocardium) is demonstrated. Nuclear cardiology studies (single photon and positron methods), two-dimensional echocardiography, and magnetic resonance imaging studies have been utilized to identify hibernating myocardium. If thallium-201 studies are performed, the use of reinjection of thallium and repeat imaging improves the sensitivity of these studies for the detection of viable myocardium. Dobutamine echocardiographic studies may have a higher specificity and positive predictive value for the subsequent improvement of regional systolic left ventricular function after revascularization than the nuclear techniques. However, thallium studies have an excellent negative predictive value. Positron emission tomography (PET) allows the simultaneous assessment of perfusion and metabolic activity; however, these studies are expensive and not widely available. Functional evaluation with PET is in its infancy. Functional cardiac magnetic resonance imaging (MRI), although not widely available yet, provides the most accurate evaluation of regional ventricular function. MRI spectroscopy may be utilized to assess myocardial viability. As acquisition times improve and "real-time" imaging becomes a reality, MRI and MRI spectroscopy will likely become very accurate tools for assessing functional reserve and metabolic activity. The selection of the most appropriate method for assessment of myocardial viability will include consideration of a patient's characteristics, the presence of coronary arterial tree amenable to revascularization techniques, the techniques available to the clinician to assess viability, and local revascularization experience in this population. The result of an individual patient's evaluation is relevant to the consideration of coronary revascularization, or if this is not possible, cardiac transplantation.

Stress echocardiography: recommendations for performance and interpretation of stress echocardiography. Stress Echocardiography Task Force of the Nomenclature and Standards Committee of the American Society of Echocardiography

Cardiovascular stress testing remains the mainstay of provocative evaluation for patients with known or suspected coronary artery disease. Stress echocardiography has become a valuable means of cardiovascular stress testing. It plays a crucial role in the initial detection of coronary disease, in determining prognosis, and in therapeutic decision making. The purpose of this document is to outline the recommended methodology for stress echocardiography with respect to personnel and equipment as well as the clinical use of this recently developed technique. Specific limitations will also be discussed.

Relation of ultrasonic tissue characterization with integrated backscatter to contractile reserve in chronic left ventricular ischemic dysfunction

Previous studies have shown that viable but stunned myocardium displays contractile reserve and exhibits cardiac cycle-dependent variations of integrated backscatter, whereas infarcted myocardium does not. The present study was designed to evaluate whether integrated backscatter imaging could be useful in identifying segments with recruitable inotropic reserve in patients with chronic left ventricular (LV) ischemic dysfunction. We studied 15 patients (mean age 59 +/- 10 years) with chronic coronary artery disease, anterior or inferior wall dysfunction, and depressed LV ejection fraction (35 +/- 12%), and 6 noncardiac control subjects (mean age 49 +/- 18 years). Cardiac cycle-dependent variations of integrated backscatter were measured in anterior and inferior segments during transesophageal echocardiography and compared with the contractile response (% wall thickening) of these segments to low doses of dobutamine (5 to 10 microg/kg/min). The average magnitude of cardiac cycle-dependent variations of integrated backscatter was greater among normally contracting segments of both patients and controls (5.67 +/- 0.88 and 5.64 +/- 2.26 dB, respectively, p = NS) than among dysfunctional segments (2.77 +/- 3.05 dB, p <0.01 vs control and remote segments). Dysfunctional segments were further categorized into those with and without dobutamine-induced contractile reserve. At baseline, systolic wall thickening was similar among segments responding to dobutamine than among those that did not (3.6 +/- 2.3% vs 2.9 +/- 1.6%, p = NS). During dobutamine, systolic wall thickening increased only in segments showing improvement in wall motion score (to 24.5 +/- 4.7%), whereas it remained unchanged in segments not responding to dobutamine (to 2.0 +/- 3.7%, p <0.01). The magnitude of resting cardiac cycle-dependent variations of integrated backscatter was larger in segments responding to dobutamine than in those with persistent dysfunction (5.31 +/- 2.06 vs 0.23 +/- 0.94 dB, p <0.01) and correlated significantly (r = 0.74, p <0.01) with systolic wall thickening during dobutamine. Our data demonstrate that resting cardiac cycle-dependent variations of integrated backscatter closely parallel contractile reserve in patients with chronic LV ischemic dysfunction. This suggests that tissue characterization with integrated backscatter could be a useful adjunct to the delineation of myocardial viability in these patients.

Nitroglycerin enhances the ability of dobutamine stress echocardiography to detect hibernating myocardium

BACKGROUND

A biphasic response of wall thickening with initial improvement and subsequent deterioration during dobutamine stress echocardiography (DSE) has been increasingly used for detection of hibernating myocardium. However, the improvement of wall thickening at low-dose DSE may be limited in hibernating myocardium by severe hypoperfusion. Nitroglycerin (NTG) improves myocardial perfusion, reduces oxygen demand, and may enhance low-dose dobutamine to improve wall thickening.

METHODS AND RESULTS

A pig model of myocardial hibernation of 24 hours to 7 days was created through severe left anterior descending coronary artery stenosis with coronary flow reductions of approximately 40%, producing severe regional left ventricular dysfunction but no infarction in seven pigs. Myocardial infarction was produced in five pigs with occlusion of the artery. DSE was performed with incremental doses with and without an NTG infusion of 50 to 100 microg/min. In the hibernating group, NTG alone improved wall thickening in the hibernating region modestly from 11.4+/-7.2% at baseline to 19.1+/-7.0%. The improvement was associated with increased regional coronary flow from 0.46+/-0.12 to 0.55+/-0.13 mL x beat(-1) x 100 g myocardium(-1) (P<.05). There was an additive effect of NTG to low-dose (2.5 to 5 microg x kg(-1) x min(-1)) dobutamine on wall thickening in the hibernating region. The improvement of wall thickening of hibernating myocardium with NTG and dobutamine, from 23.7+/-11.1% to 31.1+/-8.9% (P<.001), was associated with an increase in regional coronary flow (P<.01). NTG did not prevent high doses of dobutamine from inducing deterioration of wall thickening in hibernating myocardium. In the infarcted group, no improvement in wall thickening was observed in infarcted regions during NTG infusion, dobutamine infusion, or the combination.

CONCLUSIONS

NTG enhances the improvement of wall thickening at low-dose dobutamine and does not prevent high-dose dobutamine from inducing ischemia in hibernating myocardium. Thus, NTG augments the biphasic response of wall thickening and improves the accuracy of DSE for detecting viable myocardium.

PET scan predicts recovery of left ventricular function after coronary artery bypass operation

BACKGROUND

Viable but hypocontractile myocardium can show functional improvement after revascularization (hibernation). It is sometimes difficult, however, to predict viability and recovery in patients with severe left ventricular function. This study sought to identify possible predictive factors of recovery of cardiac function after revascularization in patients with three-vessel disease.

METHODS

Positron emission tomography (fluoro-18-deoxyglucose uptake for metabolism; nitrogen 13-labeled ammonia for flow) and equilibrium-gated nuclear angiography (for the global ejection fraction) were performed in 59 patients with three-vessel disease before and after undergoing coronary artery bypass grafting. The positron emission tomographic data were expressed as match normal (flow and metabolism normal), mismatch (low flow, high metabolism), match viable (moderate decrease in flow and metabolism), and match necrosis (low flow and metabolism).

RESULTS

Stepwise logistic regression analysis showed that only mismatch regions played a significant role in predicting postoperative improvement in function (p = 0.019). There were 1.7 +/- 1.5 mismatch regions in 31 patients who showed an improvement in their ejection fraction (0.47 +/- 0.14 versus 0.58 +/- 0.11; mean +/- standard deviation) versus 0.8 +/- 1.0 mismatch regions (p = 0.017) in patients who did not show recovery. There was more pronounced functional improvement with increasing numbers of mismatch regions, and patients with at least one mismatch region had a high likelihood of recovery (p < 0.001). In patients with a very low preoperative ejection fraction and two or more mismatch regions, there was early significant recovery (0.27 +/- 0.08 versus 0.46 +/- 0.06; p = 0.009).

CONCLUSIONS

At least one mismatch region must be present for there to be a postoperative functional benefit. When a low left ventricular ejection fraction is associated with mismatch, early recovery is substantial.

Accuracy of currently available techniques for prediction of functional recovery after revascularization in patients with left ventricular dysfunction due to chronic coronary artery disease: comparison of pooled data

OBJECTIVES

This study evaluated the relative merits of the most frequently used techniques for predicting improvement in regional contractile function after coronary revascularization in patients with left ventricular dysfunction due to chronic coronary artery disease.

BACKGROUND

Several techniques have been proposed for predicting improvement in regional contractile function after revascularization, including thallium-201 (Tl-201) stress-redistribution-reinjection, Tl-201 rest-redistribution, fluorine-18 fluorodeoxyglucose with positron emission tomography, technetium-99m sestamibi imaging and low dose dobutamine echocardiography (LDDE).

METHODS

A systematic review of all reports on prediction of functional recovery after revascularization in patients with chronic coronary artery disease (published between 1980 and March 1997) revealed 37 with sufficient details for calculating the sensitivity and specificity of each imaging modality. From the pooled data, 95% and 99% confidence intervals were also calculated.

RESULTS

Sensitivity for predicting regional functional recovery after revascularization was high for all techniques. The specificity of both Tl-201 protocols was significantly lower (p < 0.05) and LDDE significantly higher (p < 0.01) than that of the other techniques.

CONCLUSIONS

Pooled analysis of 37 studies showed that although all techniques accurately identify segments with improved contractile function after revascularization, the Tl-201 protocols may overestimate functional recovery. The evidence available thus far indicates that LDDE appears to have the highest predictive accuracy.

Echocardiography for the assessment of myocardial viability

The identification of viable myocardium in the setting of acute myocardial infarction or chronic coronary artery disease with reduced left ventricular function has important prognostic and therapeutic implications. Many noninvasive methods have been used to assess viability, and recently, dobutamine stress echocardiography has been studied for this purpose. Dobutamine stress echocardiography is a safe, accessible, and relatively inexpensive technique. Moreover, its accuracy for detecting viability approaches that of positron emission tomography and thallium scintigraphy. In addition to dobutamine stress echocardiography, other echocardiographic techniques, such as myocardial contrast echocardiography and dipyridamole stress echocardiography, are being developed to delineate viability. In the future, echocardiographic methods may identify viability with enough accuracy to allow us to better select patients for revascularization procedures when the indications are otherwise unclear.

[II. Role of Doppler echocardiography in the management of chronic ischemic cardiopathy]

Doppler echocardiography is a simple, fast and non-invasive method to identify abnormal regional and global left ventricular function. One could consider this method the best application for this end within the techniques of imaging. This chapter reviews the role of Doppler echocardiography in the management of chronic coronary artery disease, as well as for studying the global and regional function at rest, as in the applications derived from their use during stress testing. Frequent techniques of stress echocardiography for the diagnosis of ischemic heart disease, their utility in the study of myocardial viability, and the establishment of recommendations for their use in clinical practice are analyzed.

Hibernating myocardium has reduced blood flow at rest that increases with low-dose dobutamine

The study of Sun and coworkers is important because (1) it provides additional data that HM has an inotropic and an attenuated coronary vasodilator reserve. They also provided data that support the conclusion that with dobutamine, the improvement of abnormal LV wall motion is real in many patients. (2) It emphasizes the possibility of a deleterious effect (infarction) of dobutamine in HM and thus the need for appropriate caution during its use. (3) It provides additional data that confirm that areas of perfusion-metabolism mismatch on PET imaging (HM) are associated with a reduced MBF at rest. However, their conclusions about areas of LV dysfunction with "normal" MBF in coronary artery disease are problematic; therefore, one must be extremely cautious about these conclusions on the basis of the data that are presented.