Online integration of intravascular ultrasound images into angiographic images

Online PC-based integration of digital intracoronary ultrasound images into angiographic images during cardiac catheterization

In recent years, intravascular ultrasound (IVUS) has evolved as an important adjunct to angiography, providing insights that are significantly altering conventional paradigms in diagnosis and therapy. However, major drawbacks in the use of IVUS relied on the fact that a heavy console had to be moved from lab to lab, and extensive time for set up and image analysis. This additional time and the decrease in patients' through-put has not been applicable in clinical practice for many labs. Our manuscript concerns a novel PC-based platform for IVUS that enables the online intergration of digital intracoronary ultrasound images into angiographic images. This new technique offers remote operation, multiple control devices and custom viewing options. The PC-based platform enables IVUS images to be viewed simultaneously from multiple vantage points in the lab, and allows for multiple user interfaces.

Relation between plaque progression and low-density lipoprotein cholesterol during aging as assessed with serial long-term (> or =12 months) follow-up intravascular ultrasound of the left main coronary artery

Because of the clinical benefit of lipid lowering in older patients, we hypothesized that the relation between low-density lipoprotein (LDL) cholesterol serum levels and coronary plaque progression may persist throughout aging. We analyzed serial intravascular ultrasound (IVUS) data of 60 left main stems (18 +/- 9 months apart) and evaluated the relation between LDL cholesterol levels and coronary plaque progression at different ages. The population (n = 60) was divided into 3 groups according to age: tertile 1 (n = 20) was a mean age of 48 +/- 6 years (median 51, range 33 to 55), tertile 2 (n = 20) was a mean age of 58 +/- 2 years (median 59, range 55 to 61), and tertile 3 (n = 20) was a mean age of 66 +/- 6 years (median 65, range 61 to 83). Between groups, there was no significant difference in non-age-related demographics, clinical data, lipid profiles, or medications (e.g., statins). There was a positive linear relation between LDL cholesterol and annual changes in plaque plus media area in all age tertiles, which was statistically significant in tertiles 2 and 3 (r = 0.56, p <0.01; r = 0.50, p <0.02) and showed a strong trend in tertile 1 (r = 0.41, p = 0.07). The estimated LDL cholesterol thresholds, which, as determined by regression analysis, would correspond to no plaque progression, were 74, 60, and 78 mg/dl, respectively, in tertiles 1, 2, and 3. In conclusion, serial IVUS data in left main coronary arteries suggest that the relation between LDL cholesterol serum levels and plaque progression persists during aging.

Relation between lipoprotein(a) and fibrinogen and serial intravascular ultrasound plaque progression in left main coronary arteries

OBJECTIVES

Patients with elevated lipoprotein(a) [Lp(a)] and fibrinogen levels have an increased risk of coronary heart disease and adverse cardiovascular events. There is evidence that coronary plaque progression is linked to a higher risk for future cardiovascular events.

BACKGROUND

There are no data demonstrating a relation between Lp(a), fibrinogen, and directly measured coronary plaque progression over time.

METHODS

We performed a retrospective analysis of serial intravascular ultrasound (IVUS) studies of 60 left main stems (18 +/- 9 months apart) to evaluate plaque progression in relation to Lp(a) and fibrinogen levels and association with adverse cardiovascular events.

RESULTS

There was a positive correlation between Lp(a) (r = 0.58; p < 0.0001), fibrinogen (r = 0.48; p < 0.0001), and changes in plaque-plus-media area. Patients with plaque progression (n = 41) had higher Lp(a) (30 +/- 26 mg/dl vs. 14 +/- 9 mg/dl; p < 0.0012) and fibrinogen (295 +/- 88 mg/dl vs. 240 +/- 72 mg/dl; p = 0.019) levels than patients with plaque regression (n = 19). Multivariate linear regression analysis showed Log Lp(a) (regression coefficient = 9.45; p = 0.0008) but not fibrinogen to be independently associated with plaque progression. A total of 19 patients suffered from adverse cardiovascular events; they had higher Lp(a) (44 +/- 30 mg/dl vs. 16 +/- 12 mg/dl; p < 0.0001) and fibrinogen (342 +/- 73 mg/dl vs. 248 +/- 76 mg/dl; p < 0.0001) levels. Multivariate logistic regression analysis showed Log Lp(a) (odds ratio 10.20, 95% confidence interval 2.36 to 44.13; p = 0.0019) and fibrinogen (odds ratio 1.01, 95% confidence interval 1.00 to 1.03; p = 0.018) were independently associated with adverse cardiovascular events.

CONCLUSIONS

Serial IVUS showed a positive correlation between Lp(a) and fibrinogen levels and plaque progression. Lp(a), but not fibrinogen, remains independently associated with plaque progression. In addition, the present data suggest a considerable incremental value of Lp(a) in predicting cardiovascular risk.

Remodeling Index Compared to Actual Vascular Remodeling in Atherosclerotic Left Main Coronary Arteries as Assessed With Long-Term (≥12 Months) Serial Intravascular Ultrasound

OBJECTIVES

We present the remodeling index (RI) versus serial intravascular ultrasound (IVUS) data.

BACKGROUND

The RI, derived by comparing lesion external elastic membrane (EEM) cross-sectional area versus the reference at one time point, is used in various IVUS studies as a substitute of true remodeling (change in EEM over time), assuming that it represents true remodeling.

METHODS

We studied 46 non-stenotic left main arteries using serial IVUS (follow-up 18 +/- 8 months). Plaques were divided into subgroups according to the follow-up RI: follow-up RI >1 (n = 27) versus follow-up RI < or =1 (n = 19).

RESULTS

Lesions with a follow-up RI >1 had an increase in lumen despite an increase in plaque because of an increase in EEM. Conversely, lesions with a follow-up RI < or =1 had a reduction in lumen as a result of both a plaque increase and EEM decrease. Overall, the follow-up RI correlated directly with changes in lesion site EEM (baseline-to-follow-up). Although there was no correlation between the follow-up RI and changes in reference EEM area, changes in reference EEM area did correlate directly with changes in lesion EEM area. In nearly 90% of lesions with a follow-up RI >1, there was a previously documented increase in EEM area. Using multivariate linear regression analysis, the follow-up RI was dependent on the baseline RI, the increase in lesion EEM area, and the decrease in reference EEM area. The follow-up RI was not dependent on changes in lesion plaque area.

CONCLUSIONS

The vast majority of left main lesions with a remodeling index >1 had evidence of a previous increase in lesion-site EEM area.

Impact of intraventricular conduction delay on coronary haemodynamics: a study with intracoronary Doppler in patients with bundle branch blocks and normal coronary arteries

AIMS

The impact of right bundle branch block (RBBB) and left bundle branch block (LBBB) on myocardial perfusion is not completely understood as data are often blurred by underlying cardiac disease. The present study investigates whether conduction delays per se affect coronary perfusion-an indirect measure of myocardial oxygen demand.

METHODS AND RESULTS

Intracoronary Doppler and ultrasound were performed in 8 patients with RBBB, 10 patients with LBBB, and 10 control subjects. All patients had angiographically normal coronary arteries and normal left ventricular function. Baseline (bAPV) and adenosine-induced hyperaemic average flow velocity and coronary flow velocity reserve (CFVR) were measured in left anterior descending arteries. Intravascular ultrasound showed no difference in lumen cross-sectional area and plaque burden between groups. Patients with RBBB and LBBB had higher bAPV values than controls (19.0 +/- 4.9, 21.9 +/- 5.1, and 14.6 +/- 2.4 cm/s, respectively; ANOVA P = 0.003). There was no difference between patients with LBBB and RBBB compared with controls in CFVR (2.8 +/- 0.5, 3.0 +/- 1.0, and 3.4 +/- 0.7, respectively; ANOVA P = 0.21).

CONCLUSION

Bundle branch blocks, in particular LBBB, are associated with an increased coronary flow velocity, which indicates enhanced myocardial oxygen demand on the basis of mechanoenergetic disturbance. This may contribute to the unfavourable outcome of patients with intraventricular conduction delay.

Determinants of coronary blood flow in humans: quantification by intracoronary Doppler and ultrasound

The direct determinants of coronary flow are lumen area and blood flow velocity; however, the precise mechanisms that control these factors are not fully understood. The aim of the present study was to assess by which mechanisms lumen area and coronary flow velocity interact with hemodynamic and morphometric factors, thereby influencing coronary flow. Intracoronary Doppler and ultrasound measurements were performed in 28 patients without coronary lumen irregularities. Flow velocity and lumen cross-sectional area were measured in the proximal segments of all three coronary arteries. Global lumen cross-sectional area and global flow were obtained by adding up the values of all three coronary arteries. Left ventricular mass was assessed by echocardiography. Stress-mass-heart rate and pressure-rate products reflecting myocardial oxygen demand were calculated. Global coronary flow increased during adenosine-induced hyperemia from 197 +/- 72 to 637 +/- 204 ml/min (P < 0.001). Global coronary flow closely correlated with the stress-mass-heart rate product (r = 0.62; P < 0.001). Looking at the two constituents of flow separately, global coronary cross-sectional area was closely related to left ventricular muscle mass (r = 0.61; P < 0.001), whereas mean coronary flow velocity at rest showed a strong linear relation with the pressure-rate product (r = 0.64; P < 0.001). There was no interaction between cross-sectional area and blood flow velocity in any of the coronary vessels. Coronary lumen size and flow velocity, the two determinants of coronary flow, are principally determined by different physiological factors. Long-term flow adaptation is achieved by an increase in coronary lumen size, whereas short-term myocardial oxygen requirements are met by changes in resting flow velocity.

Relationship between cardiovascular risk as predicted by established risk scores versus plaque progression as measured by serial intravascular ultrasound in left main coronary arteries

BACKGROUND

Intravascular ultrasound (IVUS) is increasingly used as an end point in studies aimed at reducing progression or inducing regression of coronary artery disease. However, data linking serial changes by IVUS with clinical outcomes are scarce.

METHODS AND RESULTS

In the absence of a validated risk score for secondary prevention, we compared 3 established risk scores for primary prevention--PROCAM, SCORE, and Framingham--with plaque progression and lumen reduction as assessed with serial IVUS (follow-up, 18+/-9 months) in atherosclerotic left main coronary arteries of 56 patients with established atherosclerosis. For all 3 algorithms, patients at highest estimated risk of events showed greater plaque progression than patients at lowest risk (P<0.05 to <0.01). There were positive linear relationships between the risk of clinical events and plaque progression (r=0.41 to 0.60; P<0.002 to <0.0001). This translated into a greater decrease in lumen dimensions with increasing risk (P<0.05, PROCAM and SCORE). Risk prediction using the PROCAM algorithm showed the strongest relation with serial IVUS. During follow-up, 18 patients suffered from adverse cardiovascular events; these patients had an annual plaque progression that was significantly greater than other patients (25.2+/-19.4% versus 5.9+/-15.6%, P<0.001).

CONCLUSIONS

There was a positive linear relationship between the estimated risk of clinical events derived from all 3 established risk-score algorithms and the extent of plaque progression measured by serial IVUS. This translated into stenosis progression (reduction in lumen dimensions) with increasing clinical risk.

Spectrum of remodeling behavior observed with serial long-term (>/=12 months) follow-up intravascular ultrasound studies in left main coronary arteries

Most intravascular ultrasound (IVUS) studies of arterial remodeling in native coronary arteries reported a remodeling index obtained at a single time point. We analyzed serial IVUS examinations, including the vessel cross-sectional area changes (remodeling behavior), of 60 hemodynamically nonstenotic left main lesions (baseline vs 18.4 +/- 9.4 months follow-up). Lumen reduction resulted from vessel reduction (sometimes despite plaque + media decrease), plaque + media increase (with or without vessel increase), or both. The percent annual changes in lumen area correlated strongly with changes in vessel (r = 0.84), but not with changes in plaque + media area. Plaques were classified as group A lesions, reflecting positive remodeling behavior (vessel changes >0), or group B lesions, reflecting negative (or intermediate) remodeling behavior (vessel changes <==0). Both groups did not differ significantly in demographics, laboratory data, and medications. Group A lesions (n = 40) more often showed plaque + media increase than group B lesions (32 of 40 [80%] vs 9 of 20 [45%]; p = 0.02). Group A lesions had, on average, mild annual lumen increase despite mild plaque + media increase, i.e, overcompensation of remodeling for plaque + media increase (vessel increase greater than plaque + media area increase, 19 of 40 [47%]). Conversely, group B lesions (n = 20) showed a significant lumen area reduction (-2.8 +/- 2.6 mm(2)/year) as a result of a decrease in vessel area only. Thus, serial long-term reduction of lumen size may result from vessel shrinkage (sometimes despite plaque decrease), plaque increase (with or without vessel increase), or both; overall, only the remodeling behavior has a significant relation to lumen changes. More than 30% of lesions show a negative remodeling behavior, which shows no relation to patient characteristics or initial plaque burden.

Relation Between Progression and Regression of Atherosclerotic Left Main Coronary Artery Disease and Serum Cholesterol Levels as Assessed With Serial Long-Term (≥12 Months) Follow-Up Intravascular Ultrasound

Background— The relation between serum lipids and risk of coronary events has been established, but there are no data demonstrating directly the relation between serum low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol versus serial changes in coronary plaque dimensions.

Methods and Results— We performed standard analyses of serial intravascular ultrasound (IVUS) studies of 60 left main coronary arteries obtained 18.3±9.4 months apart to evaluate progression and regression of mild atherosclerotic plaques in relation to serum cholesterol levels. Overall, there was (1) a positive linear relation between LDL cholesterol and the annual changes in plaque plus media (P&M) cross-sectional area (CSA) ( r =0.41, P <0.0001) with (2) an LDL value of 75 mg/dL as the cutoff when regression analysis predicted on average no annual P&M CSA increase; (3) an inverse relation between HDL cholesterol and annual changes in P&M CSA ( r =−0.30, P <0.02); (4) an inverse relation between LDL cholesterol and annual changes in lumen CSA ( r =−0.32, P <0.01); and (5) no relation between LDL and HDL cholesterol and the annual changes in total arterial CSA (remodeling). Despite similar baseline IVUS characteristics, patients with an LDL cholesterol level ≥120 mg/dL showed more annual P&M CSA progression and lumen reduction than patients with lower LDL cholesterol.

Conclusions— There is a positive linear relation between LDL cholesterol and annual changes in plaque size, with an LDL value of 75 mg/dL predicting, on average, no plaque progression. HDL cholesterol shows an inverse relation with annual changes in plaque size.

Safety of intracoronary Doppler flow measurement

BACKGROUND

With the introduction of Doppler-tipped guide wires, intracoronary Doppler flow measurement has been increasingly accepted as an additional diagnostic approach in the catheterization laboratory. However, the safety of intracoronary Doppler flow measurement has not been well-investigated. The purpose of our study was to evaluate the safety of intracoronary Doppler flow measurement using the Doppler FloWire (Cardiometrics, Mountain View, Calif).

METHODS AND RESULTS

A total of 906 patients were examined by intracoronary Doppler with a 0.014-inch or an 0.018-inch Doppler FloWire. For coronary flow reserve measurement, intracoronary injection of adenosine or papaverine was used. Of the patients studied, 77 were cardiac transplant recipients and 829 were patients who had not received a transplant, of whom 617 had undergone diagnostic coronary procedures and 212 had coronary interventions. In 27 (2.98%) of 906 patients adverse cardiac events were observed. Fifteen (1.66%) of 906 patients had severe transient bradycardia develop (asystole or second- to third-degree atrioventricular block) after intracoronary administration of adenosine, 14 of which occurred in the right coronary artery and 1 in the left anterior descending artery. Nine (0.99%) of 906 patients had coronary spasm during the passage of the Doppler wire (5 in the right coronary artery, 4 in the left anterior descending artery). Two (0.22%) of 906 patients had ventricular fibrillation during the procedure. Hypotension with bradycardia and ventricular extrasystole each occurred in 1 (0.11%) of 906 patients. The incidence of complication was significantly higher in transplant recipients than in patients who underwent either diagnostic or interventional procedures (12.99% vs 2.43% vs 0.94%, P <.001). The Doppler measurements in the right coronary artery were associated with a higher incidence of complications, especially bradycardia, compared with the left anterior descending and the left circumflex arteries (right coronary, 5.87% vs left anterior descending, 1.05% vs left circumflex, 0.17%; P <.001). All complications were cured medically.

CONCLUSION

Intracoronary Doppler flow measurement with Doppler wires and intracoronary administration of adenosine is a safe method. However, severe complications such as bradycardia and coronary spasm can occur. Attention should be paid to the examination of the right coronary artery, especially in heart transplant recipients.

Corrected coronary flow velocity reserve: a new concept for assessing coronary perfusion

OBJECTIVES

In order to limit the variability of coronary flow velocity reserve (CFVR), we analyzed which factors independently affect CFVR and established a new parameter integrating these factors.

BACKGROUND

Coronary flow velocity reserve (CFVR) is a frequently used parameter for evaluating the physiological significance of epicardial stenosis and microvascular function. Since CFVR measurements are done in substantially different hemodynamic and clinical situations, interpretation of CFVR requires correction for major influencing factors.

METHODS

In 141 patients with angina-like symptoms and angiographically unobstructed coronary arteries, intracoronary Doppler measurements were performed in at least two coronary vessels. Coronary flow velocity reserve was calculated as the ratio of hyperemic average peak velocity (hAPV), after intracoronary bolus of adenosine, to baseline average peak velocity (bAPV).

RESULTS

Analysis of covariance revealed that only bAPV (p < 0.0001) and age (p < 0.0001) were independent factors influencing CFVR. Based on a regression model for estimation of predicted CFVR values, individual CFVR values (CFVRind) obtained at different bAPV and age were transformed in corrected CFVR values (CFVRcorr) by relating them to a mean bAPV of 15 cm/s and a mean age of 55 years. The transformation from CFVRind into CFVRcorr for the left anterior descending artery can be done by using the following equation: CFVRcorr = 2.85*CFVR(ind)*10(0.48*log(bAPV)+(0.0025*age)-1.16). When applying this new parameter to conditions assumed to cause microvascular dysfunction, analysis showed that only patients with diabetes showed a significant decrease of traditional CFVR and CFVRcorr, whereas a history of hypertension and current smoking habit had no influence on CFVRcorr.

CONCLUSIONS

The concept of CFVRcorr standardizes CFVR for bAPV and age as the major physiological determinants. Especially in patients with microvascular dysfunction, this approach may help to discriminate between conditions directly affecting vasodilator reserve and conditions primarily affecting bAPV.

Prevalence of microvascular disease in patients with significant coronary artery disease

Coronary flow velocity reserve (CFVR) measurement using intracoronary Doppler techniques has been increasing accepted for the assessment of physiological significance of epicardial stenosis and the functional changes after coronary interventions. However, large discrepancy exists concerning the acute changes of CFVR immediately after intervention. The purpose of this study was to investigate the prevalence of microvascular dysfunction in patients with significant coronary artery disease. Intracoronary Doppler flow measurements were performed in a total of 212 patients who underwent coronary interventions because of significant epicardial stenosis using 0.014" Doppler flow wire (Cardiometrics, Inc, Mountain View, CA). Intracoronary bolus injection of adenosine (12 micrograms for the right coronary and 18 micrograms for the left coronary arteries) was used to induce hyperemic reaction. CFVR was registered as the ratio of average peak velocity during hyperemia (hAPV) to at baseline (bAPV). Successful coronary interventions either by percutaneous transluminal coronary balloon angioplasty (PTCA) or by stenting could significantly improve the CFVR. In 80 patients with PTCA, the bAPV elevated from 16.6 +/- 2.1 cm/s to 20.6 +/- 13.4 cm/s and hAPV from 30.1 +/- 15.9 cm/s to 45.2 +/- 17.7 cm/s (both p < 0.001) with PTCA and the CFVR increased from 1.94 +/- 0.78 to 2.58 +/- 0.87 correspondingly (p < 0.001). Significant elevation of coronary flow parameters were also found in 132 patients with subsequent stent implantation (bAPV from 15.3 +/- 6.7 cm/s to 18.7 +/- 9.1 cm/s, hAPV from 28.7 +/- 14.4 cm/s to 44.3 +/- 17.7 cm/s and CFVR from 1.90 +/- 0.70 to 2.59 +/- 0.87, all p < 0.001). Reduction of CFVR (< 3.0) after intervention still existed in 46 (61.3%) of 80 patients after PTCA and 88 (66.7%) of 132 patients after stenting. Moreover, CFVR < 3.0 were found in 50 (45.9%) of 109 reference vessels in patients with single vessel disease. Significant improvement of coronary flow velocity and coronary flow velocity reserve could be obtained after successful angioplasty. However, microvascualr dysfunction existed in a large proportion of patients either in normal reference vessels or in target vessels after interventions.

Does remodeling occur in the diseased human saphenous vein bypass grafts? An intravascular ultrasound study

BACKGROUND

Coronary artery remodeling is a common phenomenon in human atherosclerotic arteries. Controversies exist concerning the presence of absence of the remodeling process in diseased human coronary saphenous vein bypass grafts. The purpose of the study was to observe the vessel and lumen dimensions in patients who had undergone saphenous vein grafting with intravascular ultrasound to find out whether the remodeling process exists in the diseased human saphenous vein bypass grafts.

METHODS

A total of 43 saphenous vein bypass grafts from 43 patients (39 males, 4 females, mean age 63+/-8 years); 1-16 years (mean 9.3+/-4.0 years) after grafting, who had not undergone previous catheter intervention, were studied using intravascular ultrasound. The vessel, lumen and plaque area were measured at the lesion segment as well as in the proximal and distal reference segments. The percent stenosis was calculated.

RESULTS

In 43 bypass grafts having severe stenosis before intervention, plaque was eccentric in 69.4% and concentric in 30.6%. No calcification was detected in 75% cases and 25% cases has mild-moderate intimal calcification. The vessel area in the lesion segment was 19.0+/-9.7 mm2, significantly larger than the proximal reference segment 12.8+/-4.0 min2 as well as the distal reference segment 12.9+/-3.6 mm2 (p < 0.001). It was also larger than that of the average area of the proximal and distal reference segments (p < 0.001). The vessel area increased in accordance with plaque area (p < 0.001). A weak relationship existed between vessel area and percent stenosis (r = 0.37, p = 0.04).

CONCLUSION

In contrary to previous findings, diseased human saphenous vein bypass grafts undergo focal compensatory enlargement (remodeling) in the presence of plaque formation. The underlying mechanism is probably similar to that in de novo atherosclerosis.