Outcomes of transcatheter vs. isolated surgical aortic valve replacement in mediastinal radiation-associated severe aortic stenosis

Introduction

Mediastinal radiation can lead to long-term cardiac sequelae, including aortic valve disease. Surgical aortic valve replacement (SAVR) is associated with poor outcomes in this population. Transcatheter aortic valve replacement (TAVR) now provides an alternative treatment strategy that may improve outcomes.

Purpose

To compare 30-day outcomes after TAVR vs. isolated SAVR for radiation-associated severe symptomatic aortic stenosis using the Society of Thoracic Surgery (STS) National Adult Cardiac Surgery Database.

Methods

We evaluated 1,668 TAVR and 2,611 isolated SAVR patients enrolled in the STS national database from July 2011 through December 2018. A propensity score for TAVR vs. SAVR was derived using a non-parsimonious logistic regression model that included 29 pre-operative variables and was used to generate a 1:1 matched cohort (NTotal=1,560). 30-day outcomes in TAVR vs. SAVR patients were compared in the matched cohort using conditional logistic regression. We also tested for temporal trends in 30-day mortality separately for TAVR and SAVR in the matched cohort, adjusted for potential confounders, to see if outcomes varied across the study period.

Results

In the propensity-matched cohort, baseline demographics, comorbidities and preoperative characteristics were balanced between the TAVR and SAVR groups. The mean age was 73.3 years and 75% were females in each group. In the propensity-matched cohort, TAVR was associated with significantly reduced 30-day all-cause [OR=0.50 (0.30–0.84), p=0.01] and cardiovascular mortality as compared to SAVR [OR=0.33 (0.14–0.78), p=0.01]. Similarly, post-operative complications occurred less in the TAVR group except for stroke/transient ischemic attack (TIA) [OR=3.17 (1.27–7.93), p=0.01] and pacemaker implantation [OR=1.71 (1.21–2.44), p=0.003] which were significantly higher with TAVR (Figure 1A). While, 30-day mortality associated with both procedures improved over the course of the study, the trend was only statistically significant in the TAVR group following adjustment for potential confounders. TAVR was consistently associated with better survival than SAVR in the matched cohort across the study period (Figure 1B).

Conclusion

Our findings suggest that TAVR is a safe alternative to SAVR for radiation-associated severe symptomatic aortic stenosis and is associated with lower 30-day mortality and post-operative complications. The risk of stroke/TIA and pacemaker implantation is higher with TAVR and should be considered when choosing therapy. Additional prospective studies to validate our findings and evaluate long-term outcomes are needed to further guide clinical decision making in this population.

Figure 1

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Funding to support acquisition of the data from the Society of Thoracic Surgery was obtained from discretionary funds available to Dr. Anju Nohria from the Cardiovascular Medicine Division.

Enhancement of adenoviral gene transfer to adult rat cardiomyocytes in vivo by immobilization and ultrasound treatment of the heart

Direct injection of adenoviral vectors into ventricular myocardium in vivo produces local transfection of cells including cardiomyocytes. The use of vectors coexpressing GFP with the gene of interest allows subsequent identification of transfected myocytes isolated from the heart some days later, and examination of their function in cell bath experiments. We have injected vectors for antisense to phospholamban, or a control virus for expression of GFP only, into adult rat heart in vivo and then removed the heart and isolated ventricular myocytes 7 days later. Brief immobilization of the ventricle during and after injection using a haemoclip increased the number of transfected rod-shaped, viable myocytes from 1.7 +/- 0.8% (n = 8) to 5.6 +/- 0.8% (n = 9). This was further increased to 13.2 +/- 1.1% (n = 8) by the application of ultrasound pulses to the site before and after injection. Phospholamban antisense increased contraction amplitude and accelerated myocyte relengthening or decline of the Ca(2+) transient in transfected myocytes, while GFP control did not. Qualitative and quantitative effects of phospholamban downregulation were comparable between in vivo and in vitro transfections. This technique will have a number of uses, including production of transfected myocytes without the problem of culture-induced changes in contractility.

Initiation of hormone replacement therapy after acute myocardial infarction is associated with more cardiac events during follow-up

OBJECTIVES

This study explored the association between the initiation of hormone replacement therapy (HRT) and early cardiac events (<1 year) in women with a recent myocardial infarction (MI).

BACKGROUND

Observational studies have linked postmenopausal hormone use with a reduced risk of death from heart disease. However, a recent randomized trial of HRT found no long-term benefit, primarily due to an increase in cardiac events in the first year.

METHODS

The Coumadin Aspirin Reinfarction Study (CARS) database contains information on HRT use and menopausal status for women with a recent MI. We classified the 1,857 postmenopausal women in CARS as prior/current HRT users if they took HRT before enrollment, new users if they began HRT during the study period or never users. We assessed the incidence of cardiac events (death, MI, unstable angina [UA]) during follow-up.

RESULTS

In our cohort, 28% (n = 524) used HRT at some point. Of these, 21% (n = 111) began HRT after their MI. New users had a higher incidence of death/MI/UA (41% vs. 28%, p = 0.001) during follow-up than never users, largely due to a higher incidence of UA (39% vs. 20%, p = 0.001). After adjustment, new users still had a significantly higher risk of death/MI/UA than never users during follow-up (relative risk [RR] = 1.44 [1.05-1.99]). Prior/current users had no excess risk of the composite end point after adjustment. Users of estrogen/progestin had a lower incidence of death/MI/UA during follow-up than users of estrogen only (RR = 0.56 [0.37-0.85]).

CONCLUSIONS

Postmenopausal women who initiated HRT after a recent MI had an increased risk of cardiac events largely due to excess UA during follow-up.

Heparin-bonded cardiopulmonary bypass circuits reduce bleeding and transfusion requirements in proximal aortic surgery

BACKGROUND

Methods to improve hemostasis in aortic surgery continue to evolve. Use of heparin-bonded cardiopulmonary bypass circuits (HBC) has been shown previously to effectively reduce bleeding and improve outcomes in coronary and valve operations.

OBJECTIVE

To evaluate the impact of HBC on bleeding and transfusion requirements in proximal aortic surgery.

METHODS

Data on 140 consecutive patients undergoing 144 operations of the proximal aorta were collected. Between July 1987 and July 1994, conventional cardiopulmonary bypass circuits (CONV) were used (n = 53). In July 1994, we switched to "tip-to-tip" HBC (n = 91). This study compared clinical outcomes and transfusion requirements between these two groups.

RESULTS

Indications for surgery, baseline characteristics, and operative profile of the study groups were similar. Overall operative mortality and reoperation for bleeding were 9% and 13%, respectively. Compared with CONV, use of HBC was associated with decreased mortality (3% vs 18%, p = 0.004), reoperation for bleeding (7% vs 24%, p = 0.005), and hospital length of hospital stay (10 +/- 11 vs 20 +/- 30 days, p = 0.002). Although the incidence of allogeneic blood transfusion was similar (HBC 75% vs CONV 87%, p = 0.12), the magnitude of blood products utilization was much lower in the HBC group (total blood products per patient: 24 +/- 29 vs 49 +/- 47 donor units, p = 0.0002). In the multivariate analyses, use of HBC was identified as an independent predictor of reduced mortality, morbidity, and reduced magnitude of allogeneic blood transfusions.

CONCLUSION

Use of HBC in proximal aortic surgery resulted in reduced bleeding and blood transfusion, improving clinical outcomes. Undoubtedly, multiple factors account for the overall improved results. However, use of HBC is an important component of an overall blood conservation strategy.

Functional alterations in adult rat myocytes after overexpression of phospholamban with use of adenovirus

An increased phospholamban (PLB)-to-sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) ratio has been suggested to contribute to the slowing of relaxation in failing human ventricle. We have used an adenoviral vector carrying the sequence for PLB to increase this ratio in isolated adult rat ventricular myocytes, and we have examined the functional consequences. With use of adenoviral vectors, the PLB content of adult rat myocytes was increased 2.73-fold, with SERCA2a levels unchanged. Maximum contraction amplitude of PLB-overexpressing myocytes was decreased to 6.9 +/- 0.3% shortening compared with 11.2 +/- 0.8% for 24-h controls (Con; P < 0.001, 5 preparations, 103 myocytes). Maximum rates of shortening and relengthening were also significantly decreased. Ca(2+) transient amplitudes were slightly depressed, and time to 50% decay of the transients was significantly increased: 237 +/- 18 (n = 14 myocytes) and 432 +/- 32 ms in Con and PLB (n = 15) myocytes, respectively (P < 0.001). The amount of Ca(2+) in the sarcoplasmic reticulum stores was reduced by 21% (P < 0.05). Relaxation was significantly slower in PLB than in Con myocytes when the Na(+)/Ca(2+) exchanger was blocked but not when sarcoplasmic reticulum Ca(2+) uptake was inhibited. Adenovirus infection with Ad.RSV.PLB was therefore able to produce functional changes in adult cardiac myocytes within 24 h, consistent with overexpression of PLB and similar to those seen in failing human heart.

Comparison of risk profile and outcomes in patients undergoing surgical and catheter-based revascularization

BACKGROUND

The effects of the randomized revascularization trials and improved strategies and techniques for coronary artery bypass graft (CABG) surgery and percutaneous transluminal catheter-based revascularization (PTCR) on current patient selection and clinical outcomes are unknown.

METHODS

We evaluated a concurrent, contemporary (1995 to 1997), and consecutive group of patients undergoing CABG (n = 982) or PTCR (n = 939) in a single institution that participated in the Bypass Angioplasty Revascularization Investigation (BARI) trial. Results are presented as percent or mean +/- SD. Compared to PTCR, patients undergoing CABG were older (66.2+/-10.7 vs. 62.0+/-11.8 years, p<0.05) with a higher incidence of hypertension (73.3% vs. 52.4%, p<0.05), diabetes (32.5% vs. 23.1%, p<0.05), active smoking (67.8% vs. 27.2%, p<0.05), prior myocardial infarction (MI)(66.8% vs. 28.5%, p<0.05), peripheral vascular disease (19.8% vs. 7.7%, p<0.05), prior cerebrovascular accident (CVA)/transient ischemic attack (TIA) (6.4% vs. 2.8%, p<0.05), and a lower ejection fraction (48.7%+/-14.5% vs. 55.3%+/-11.7%, p<0.05). The presenting functional class and incidence of female gender were similar for both revascularization strategies.

RESULTS

Compared to patients undergoing CABG, those undergoing PTCR were more likely to have single or two vessel coronary artery disease (88.6% vs. 23.1%, p<0.001) and had fewer vessels revascularized per patient (1.08+/-0.30 vs. 3.5+/-0.98, p<0.001). Outcomes were comparable for CABG and PTCR with a similar incidence of death (1.0% vs. 0.9%, NS), renal insufficiency (0.7% vs. 0.6%, NS), and CVA/TIA (0.9% vs. 0.3%, NS). Patients undergoing CABG had a higher incidence of pulmonary complications (5.2% vs. 1.0%, p<0.05), a lower incidence of periprocedural MI (1.1% vs. 4.1%, p<0.05) and major complication (5.9% vs. 9.4%, p<0.05), but longer hospital stays (6.5+/-5.1 vs. 3.1+/-2.6 days, p<0.05).

CONCLUSIONS

Despite higher clinical and angiographic risk profiles in patients undergoing CABG, clinical results, morbidity, and mortality were comparable to those of PTCR. With evolving techniques, continued reevaluation of indications and outcomes are necessary.

The role of cAMP in the frequency-dependent changes in contraction of guinea-pig cardiomyocytes

OBJECTIVES

beta-Receptor desensitisation, low basal cAMP, and a negative force-frequency relationship are characteristic changes in human heart failure. Isolated cardiomyocytes from noradrenaline-treated guinea pigs also show these features. We tested the hypothesis that low basal cAMP underlies the loss of contractile response to increasing stimulation frequency in this model.

METHODS

Isolated cardiomyocytes were obtained from noradrenaline-treated (NA) and sham-operated (SHAM) guinea pigs. They were stimulated from 0.1-2 Hz and contraction amplitude was monitored with a video edge-detection system.

RESULTS

NA cells had less positive amplitude-frequency responses (AFR) compared to SHAMs at 2 mM (P = 0.002, n = 17), or midrange Ca2+ concentrations (EC40-EC60) (P < 0.001, n = 13). When the cAMP agonist, 8-CPT-cAMP (CPT, 10 microM) or high Ca2+ (above EC75) was added to NA cells the AFR was normalised to that of SHAM myocytes (NA vs. SHAM P = ns). In control experiments the cAMP antagonists, Rp-cAMPS (Rpc) and Rp-8-CPT-cAMPS (Rp8, 100 microM), blocked the positive inotropic effects of CPT at 0.5 Hz (control pD2 = 4.36 +/- 0.06, Rp8 pD2 = 3.68 +/- 0.08, P < 0.0001), n = 6 paired). Rpc (100 microM) completely but reversibly blocked the effect of maximal isoprenaline in control experiments (P < 0.0001). Neither antagonist reduced the AFR compared to time-matched controls (P = ns, n = 6). Blockade of SERCA2a with thapsigargin resulted in a significant reduction in the AFR (ANOVA P < 0.0001).

CONCLUSIONS

The results are consistent with sarcoplasmic reticulum (SR) function being a more important determinant of the amplitude-frequency relationship than tonic levels of cAMP under basal conditions. Reversal of AFR depression by CPT may result from stimulation of SR Ca2+ uptake.

Effect of anticoagulation protocol on outcome in patients undergoing CABG with heparin-bonded cardiopulmonary bypass circuits

BACKGROUND

We have demonstrated that the use of heparin-bonded cardiopulmonary bypass circuits (HBCs) combined with a lower anticoagulation protocol as an adjunct to an integrated blood conservation strategy decreases the incidence and magnitude of homologous transfusion and improves clinical outcome in patients undergoing primary coronary artery bypass grafting. It is not known whether it is the lower anticoagulation protocol that influences outcome in patients treated with HBCs. Furthermore, the thrombogenic risk of using lower anticoagulation with HBCs still is debated.

METHODS

To answer these questions, a prospective randomized study was conducted in which 244 patients undergoing primary coronary artery bypass grafting were treated with HBCs and randomized to undergo either a full (activated clotting time, > 450 seconds) or a lower (activated clotting time, > 250 seconds) anticoagulation protocol. In addition to clinical outcome, levels of thrombin generation markers during and after cardiopulmonary bypass were assessed in a consecutive subset of 58 patients (full anticoagulation profile = 28, lower anticoagulation profile = 30) by measuring thrombin-antithrombin complexes and prothrombin fragment 1.2. Levels of these markers also were correlated with the activated clotting time during cardiopulmonary bypass.

RESULTS

Preoperative and intraoperative risk profiles and other characteristics were similar in both groups, with more than 60% of patients undergoing nonelective operation. Compared with the full anticoagulation protocol group, patients in the lower anticoagulation protocol group were less likely to require blood products (24.2% versus 35.8%, respectively; p = 0.047) and received substantially fewer homologous donor units (0.50 +/- 0.92 versus 1.08 +/- 2.10 U, respectively; p = 0.005). Clinical outcomes were uniformly outstanding (but similar) in both treatment groups, with a modest reduction in the length of the hospital stay in the lower anticoagulation protocol group (5.26 +/- 1.23 versus 5.63 +/- 1.73 days, respectively; p = 0.05). The use of HBCs with a lower anticoagulation protocol was not associated with any adverse clinical events. Thrombin generation increased during cardiopulmonary bypass in both treatment groups, but was unrelated to the anticoagulation protocol or the activated clotting time (r2 = 0.03). No differences between the full and lower anticoagulation protocol groups were noted in the number of microemboli detected by transcranial Doppler analyses during cardiopulmonary bypass (n = 40) or in the postoperative neurologic and neuropsychologic outcomes (n = 30).

CONCLUSIONS

This study definitively demonstrates that, when used appropriately, patients who are treated with HBCs and a lower anticoagulation protocol have a lower incidence and magnitude of homologous transfusion and are not at any added risk for clinical, hematologic (thrombin-antithrombin complex and fragment 1.2 measurements), or microscopic (transcranial Doppler analyses) thromboembolic complications or for neurologic or neuropsychologic deficits.

Heparin-bonded circuits improve clinical outcomes in emergency coronary artery bypass grafting

Compared to patients undergoing elective or urgent coronary artery bypass grafting (CABG), those undergoing emergency CABG (EM-CABG) have a higher morbidity and mortality. The use of heparin-bonded circuits (HBC) has been shown to improve clinical outcomes in nonemergent CABG patients. It is not known, however, whether the improved hemostasis and attenuation of the inflammatory response to cardiopulmonary bypass, conferred by HBC, can overcome the high incidence of comorbid risk factors in (EM-CABG) patients and improve their outcomes. A retrospective analysis of 206 consecutive patients undergoing EM-CABG over 4 years (1993-1997) at one institution was performed. Eighty-one patients were treated with conventional non-heparin-bonded circuits (NHBC) with full anticoagulation protocol (FAP, activated clotting time [ACT] > 480 sec); 125 patients were treated with HBC and a lower anticoagulation protocol (LAP, ACT > 280 seconds). Outcomes and results were collected prospectively and are presented as mean +/- SD. Preoperative risk profiles were similar in both treatment groups. Postoperatively, compared with the NHBC group, patients treated with HBC/LAP required fewer homologous donor units (4.1 +/- 10.7 vs 8.2 +/- 13.6 units, p = 0.005), were less likely to require inotropic support (18.6% vs 38.3%, p = 0.005), and had a lower incidence of perioperative myocardial infarction (MI, 3.2% vs 12.3%, p = 0.04) and pulmonary complications (4.0% vs 12.3%, p = 0.04). The use of HBC/LAP resulted in a decreased incidence of postoperative complications (12.8% vs 28.4%, p = 0.01, odds ratio 0.37 with 95% confidence interval [CI] 0.18-0.76). This resulted in a shorter duration of ventilatory support (30.5 +/- 54.0 vs 72.8 +/- 16.7 hours, p = 0.009), ICU stay (38.2 +/- 36.5 vs 91.5 +/- 68.7 hours, p = 0.009), hospital stay (8.0 +/- 7.1 vs 11.0 +/- 8.9 days, p = 0.008), and therefore cost. In conclusion, the use of HBC/LAP in EM-CABG resulted in a reduction of homologous transfusion and postoperative complications associated with decreased hospital stays and cost.

The effect of alterations to action potential duration on beta-adrenoceptor-mediated aftercontractions in human and guinea-pig ventricular myocytes

Aftercontractions induced by beta-adrenoceptor stimulation in human and guinea-pig cardiomyocytes may be related to changes in action potential duration (APD). We investigated the effects of altering APD during the occurrence of isoproterenol-induced aftercontractions, using the KATP channel openers cromakalim and lemakalim or the action potential voltage clamp technique, in guinea-pig and human ventricular cardiomyocytes. Contractile responses were measured at 32 degrees C using a video-based edge-detection system. In guinea-pig myocytes, action potentials, Indo-1 fluorescence and contraction were measured at 22 degrees C. Isoproterenol (< or = 12 nM) had variable effects on APD but induced aftercontractions, the majority (14/19 cells) of which occurred during the action potential. Short action potentials were produced using K+ channel openers. These compounds reduced or completely abolished the isoproterenol-induced aftercontractions. Increasing isoproterenol in the presence of K+ channel opener restored the main contraction to a level similar to or above those with isoproterenol alone, but without the reappearance of aftercontractions. When cells were stimulated to contract under action potential voltage clamp, isoproterenol-induced aftercontractions were abolished by voltage clamping with action potentials of short duration. It was possible to induce aftercontractions in some cells without application of isoproterenol if voltage clamp-imposed action potentials of very long duration were used. These aftercontractions were also abolished by shortening action potential duration. We conclude that K+ channel openers or the imposition of action potentials of short duration can dissociate positively inotropic beta-adrenoceptor stimulation from aftercontraction formation and that action potentials of long duration can be pro-arrhythmic.

Twenty-four hour nurse practitioner service in the accident and emergency department

This paper discusses the introduction of a 24-h nurse practitioner service in a major accident and emergency department and monitors it over a 3-month period. The paper provides a description of the activities of the nurse practitioners and a critical evaluation of their role. It shows that every major accident and emergency department can set up a 24-h nurse practitioner scheme and the organization of such a scheme can be very simple. This is the first article to look at a 24-h service.

The role of Gi-proteins and beta-adrenoceptors in the age-related decline of contraction in guinea-pig ventricular myocytes

A decline in contractility in myocytes from ageing guinea-pig hearts was demonstrated, which is more pronounced for maximum beta-adrenoceptor-stimulated activity than contraction in high Ca2+. In this study the role of the inhibitory G-proteins (Gi) in this process was investigated. Comparisons were made between young (Y, < 400 g, < 4 weeks), adult (A. > 600 g, > 8 weeks) and senescent guinea pigs (S, 58-65 weeks, 1136 +/- 30 g). Gi alpha activity, detected by pertussis toxin-catalysed ADP ribosylation, was significantly increased in senescent compared to young animals, but immunodetectable levels of Gi alpha were unchanged, beta-adrenoceptor number was decreased by 27% in senescent compared with young animals (P < 0.002). Pertussis toxin treatment increased the maximum response to isoproterenol in contacting myocytes so that there was no longer any significant decline with age. Maximum contraction amplitudes (sarcomere length change, micron) with isoproterenol before pertussis toxin were 0.144 +/- 0.011 (Y, n = 22 animals), 0.104 +/- 0.009 (A. 18) and 0.098 +/- 0.009 (S. 14), P < 0.01 by analysis of variance (ANOVA). Following toxin treatment amplitudes were 0.140 +/- 0.012 (Y. 12), 0.117 +/- 0.010 (A. 10) and 0.117 +/- 0.018 (S. 8), P = N.S. Pertussis toxin treatment also reversed the effects of ageing on contraction and relaxation velocity in isoproterenol. In contrast, the effect of age on contraction amplitude or velocity in maximum Ca2+ was more pronounced after toxin treatment. The EC50 value for isoproterenol increased with age: pertussis treatment decreased the EC50 in each group, but the effect was especially pronounced for senescent animals. There was no significant difference in the concentration-response curves for the negative inotropic effect of adenosine (in the presence of isoprotenerol) between the three age groups before toxin treatment. All effects of adenosine were abolished after pertussis exposure. We conclude that increased Gi alpha activity is likely to contribute to the decreased response to isoproterenol, but not to high Ca2+, in myocytes from ageing guinea-pigs.

Tachycardia-induced failure alters contractile properties of canine ventricular myocytes

OBJECTIVE

Rapid cardiac pacing has been used as a model for experimentally-induced cardiomyopathy. However, its relevance to human heart failure is not clear at present because little is known about changes in size and function of ventricular myocytes. We have therefore studied the responses to graded increases in frequency and calcium in canine ventricular myocytes from failing hearts. The aim of our study was to evaluate the resemblance between canine pacing-induced and human end-stage heart failure.

METHODS

Myocytes were isolated from the left ventricular wall of dogs that were in heart failure after 6 weeks of pacing at 250 beats/min. Cell shortening was measured by edge detection.

RESULTS

Clinical signs of failure included dyspnea, ascites, and heart dilatation; the hemodynamic parameters were: LVdP/dtmax 1613 +/- 149 vs. 4713 +/- 304 mmHg/s in 6 control dogs; LVEDP 17.2 +/- 4.4 vs 5.6 +/- 1.1 mmHg; LV volume 60.5 +/- 6.2 vs. 30-35 ml. Myocytes from failing hearts were longer and thinner than those from controls (from factor: 0.40 +/- 0.01 vs. 0.47 +/- 0.01, P < 0.001, > 30 cells/heart). With 6 mM Ca2+ and at 0.5 Hz, contraction amplitude was significantly attenuated in myocytes from failing hearts: 6.6 +/- 0.9% cell shortening vs. 10.0 +/- 0.8% in controls (P < 0.05). This deficit was exacerbated at higher stimulation rates. Time-to-peak contraction and time-to-50% relaxation were not altered. There was no difference in sensitivity to thapsigargin.

CONCLUSION

As with cells from human failing hearts, contraction amplitude showed rate-dependent depression in this animal model, whereas features like slowing of contraction and relaxation and reduced sensitivity to thapsigargin, were not reproduced.

Heparin-bonded circuits with a reduced anticoagulation protocol in primary CABG: a prospective, randomized study

BACKGROUND

A substantial proportion of patients undergoing primary coronary revascularization require homologous transfusions. To address this problem, a comprehensive strategy to diminish perioperative blood loss was developed.

METHODS

A prospective randomized trial was undertaken to test the hypothesis that "tip-to-tip" heparin-bonded cardiopulmonary bypass circuits (HBC) can further enhance blood conservation and clinical outcomes in patients undergoing primary coronary artery bypass grafting. Two hundred thirty-four patients were treated with either HBC and lower anticoagulation therapy (activated clotting time > 280 seconds) or with conventional, nonheparin-bonded circuits and full anticoagulation therapy (activated clotting time > 480 seconds).

RESULTS

Preoperative and intraoperative risk profiles and characteristics were similar in both groups, with 69.7% of the patients undergoing nonelective coronary artery bypass grafting. Compared with the group with nonheparin-bonded circuits, patients treated with HBC had a lower chest tube output in the first 24 hours (561 +/- 257 versus 651 +/- 403; p = 0.04), were less likely to receive blood products (31.6% versus 47.9%; p = 0.01), and required substantially fewer homologous donor units (1.98 +/- 4.8 versus 4.29 +/- 10.1; p = 0.029). Patients treated with HBC required a shorter duration of ventilatory support (13.2 +/- 16.9 versus 23.4 +/- 50.0 hours; p = 0.04), spent less time in the surgical intensive care unit (20.7 +/- 17.4 versus 35.5 +/- 61.7 hours; p = 0.01), spent fewer days in the hospital (6.0 +/- 2.5 versus 7.3 +/- 5.2 days; p = 0.02), and had fewer postoperative complications (25.6% versus 39.3%; p = 0.03). The use of HBC with a lower anticoagulation protocol was not associated with any adverse events.

CONCLUSIONS

This study demonstrates that the use of HBC with a lower anticoagulation protocol in primary coronary artery bypass grafting safely and effectively reduces the incidence and magnitude of homologous transfusion, the duration of ventilation, and surgical intensive care unit and hospital stays.

Acceleration of contraction by beta-adrenoceptor stimulation is greater in ventricular myocytes from failing than non-failing human hearts

Myocytes from failing human ventricle contract and relax more slowly than those from non-failing. This has been suggested to result from the lowering of basal cyclic AMP level in failing myocardium, and the consequent withdrawal of a tonic lusitropic effect. We present data to support this hypothesis by demonstrating that the acceleration of contraction and relaxation by beta-adrenoceptor stimulation is greater in myocytes from failing than non-failing heart. This is despite the desensitisation of the inotropic effect of isoprenaline in the same failing cells. Following beta-adrenoceptor stimulation, speeds of contraction and relaxation are normalised in myocytes from failing heart, with final values not significantly different from non-failing.

Cell geometry and contractile abnormalities of myocytes from failing human left ventricle

OBJECTIVES

Systolic and diastolic dysfunction of the failing human heart may be due to changes in myocyte function, or to extracellular influences such as necrosis, fibrosis or repositioning of viable cells. In order to determine the contribution of cellular factors we have characterised the contraction amplitudes, and contraction and relaxation velocities of single myocytes isolated from failing human left ventricle.

METHODS

Myocytes were enzymatically isolated from the left ventricles of 42 subjects, superfused at 32 degrees C and paced at 0.2 Hz. Using a video/edge tracking system we obtained contraction amplitude and contraction and relaxation velocities as well as times to peak contraction (TTP) and to 50% and 90% relaxation (R50 and R90). Concentration-response curves to Ca2+ were constructed for each cell.

RESULTS

There was little difference in contraction amplitude at any Ca2+ concentration between cells from failing and non-failing hearts at this low frequency. At maximally activating Ca2+ concentrations (6-20 mM) there was a 30% slowing of relaxation velocity in myocytes from patients with both mild-moderate (P < 0.001) and severe (P < 0.001) congestive heart failure. Contraction and relaxation times were increased in myocytes from failing hearts [TTP: 0.46 +/- 0.02 s (n = 34 patients) vs. 0.35 +/- 0.02 s (n = 6), P < 0.01 and R50: 0.25 +/- 0.02 s (n = 34) vs. 0.16 +/- 0.02 s (n = 6), P < 0.001]. Impaired relaxation was seen with most etiologies, including ischemic and dilated cardiomyopathies and mitral valve disease. Myocytes from failing hypertrophied ventricles were more severely affected than those from failing non-hypertrophied hearts for both contraction and relaxation velocities. Cells from failing hypertrophied ventricles had a significantly larger area than from non-failing or failing non-hypertrophied ventricles, although cell length and sarcomere length were similar between groups. Larger myocytes did not show a more pronounced change in relaxation velocity than normally sized cells from the same hypertrophied ventricle.

CONCLUSIONS

Significant impairment of relaxation can be observed in ventricular myocytes from failing human heart under conditions where contraction amplitude appears normal. The defect is not confined to one etiology of disease, but is exacerbated during hypertrophy. An increase in cell size, although observed in myocytes from hypertrophied ventricle, does not itself account for changes in relaxation. Cellular changes contribute to diastolic dysfunction in the failing human heart.

Decreased contractile responses to isoproterenol in isolated cardiac myocytes from aging guinea-pigs

We have characterized the age-related changes of contractility and beta-adrenoceptor function in isolated cardiac myocytes from guinea-pigs. We used either adult animals from 2 to 14 weeks of age, where body weight increases linearly with age, or senescent ones aged between 53-65 weeks. There was some indication of a decrease in contractility in maximum Ca2+ with age, with significant differences between a young (< or = 4 weeks, weight < 400 g) and aged (> or = 8 weeks, weight > 600 g) group in contraction amplitude expressed as percentage shortening (but not when expressed as micron change in length) or contraction and relaxation velocities. This decline was continued into senescence, and ANOVA showed a significant difference between the three groups for contraction amplitude (percentage shortening, 12.2 +/- 0.9%, young, n = 31; 9.5 +/- 0.6%, n = 28 aged; 6.7 +/- 0.8%, n = 6, senescent; P = 0.005), and contraction or relaxation velocities (P < 0.001). There was a more pronounced decline in maximum response to isoproterenol with age. ANOVA for the maximum isoproterenol response for the three divisions showed significant differences for percentage shortening (11.8 +/- 0.7%, n = 30, young; 7.9 +/- 0.5%, n-28, aged and 5.5 +/- 1.1%, n = 6, senescent; P < 0.001), velocities of contraction (P < 0.001) and relaxation (P < 0.001), and normalized velocities of contraction (P < 0.001) and relaxation (P < 0.01) at maximum isoproterenol, as well as in ISO EC50 (P < 0.001) and isoproterenol/Ca2+ ratio (P < 0.02). A general decrease in contractility of the myocyte occurs as the animal ages, with maximum contraction amplitude being reduced and velocity of contraction and relaxation slowed. The effect was more pronounced for beta-adrenoceptor stimulation than for high Ca2+, suggesting a specific lesion in the adenylate cyclase related pathway. Much of the change occurred between the young adult (< or = 4 weeks) and the aged adult (> or = 8 weeks), although the trend was continued in senescent animals (> 52 weeks).

Characteristics of myocytes isolated from hearts of renovascular hypertensive guinea pigs

A model of renovascular hypertension has been developed in the guinea pig using the Goldblatt (2-kidney, 1-clip) operation. Systolic and diastolic blood pressures were significantly increased 3 and 7 wk after the operation, but levels fell to control values at 11 wk. The two-dimensional areas of myocytes isolated from the hearts of Goldblatt-operated (GB) animals were larger than those in control cells at 3 wk (cf. 3,397 +/- 87 and 2,208 +/- 125 microns 2, P < 0.01), and the difference was maintained at 7 and 11 wk. No change in cell contraction or relaxation characteristics were seen at either 3 or 7 wk after clipping. Myocytes from the 11-wk GB group showed a significantly reduced contraction amplitude and velocity at 32 degrees C in maximally activating Ca2+ or isoproterenol concentrations (%cell shortening in Ca2+, cf. 6.8 +/- 0.4 and 10.0 +/- 0.9, P < 0.01). Concentrations eliciting 50% of maximal response for Ca2+ or isoproterenol were unchanged, as was the ratio of isoproterenol to Ca2+ effect in the same cell. Increases in time to peak contraction (TTP) and time to 50% relaxation (R50) were observed in 11-wk GB myocytes, but only at room temperature. There was no lengthening of TTP or R50 of the Ca2+ transient, nor was there any change in Ca2+ current density or inactivation kinetics in these myocytes.

Isolated ventricular myocytes from failing and non-failing human heart; the relation of age and clinical status of patients to isoproterenol response

Single cardiac myocytes were isolated from the ventricles of failing and non-failing human hearts. The contraction amplitude, time-to-peak shortening and time to 50% and 90% relaxation were measured in cells stimulated at 0.2 Hz at 32 degrees C. The effects of increasing extracellular calcium and isoproterenol were investigated using cumulative concentration/response curves. Maximum contraction amplitude in high calcium or velocities of contraction or relaxation were not impaired in cells from failing hearts. Beta-adrenoceptor function in a single cell was assessed by the maximum contraction amplitude in the presence of isoproterenol relative to that with high calcium in the same cell (isoproterenol/calcium ratio). A decrease in the isoproterenol/calcium ratio correlated positively with an increase in the isoproterenol EC50 (concentration for half-maximal effect) for a cell (P less than 0.02, n = 39). The isoproterenol/calcium ratio in left ventricular myocytes decreased with increasing severity of disease, correlating with failure as defined by New York Heart Association class (P less than 0.001, n = 26 patients), left ventricular ejection fraction (P less than 0.001, n = 24), left ventricular end diastolic pressure (P less than 0.05, n = 21) and amount of diuretics prescribed (P less than 0.001, n = 26). In right ventricular myocytes, only increasing NYHA class correlated with decreasing isoproterenol/calcium ratios. There was a correlation of the isoproterenol/calcium ratio between right and left ventricular cells from patients with ischemic heart disease (P less than 0.05), n = 11). Beta-adrenoceptor subsensitivity occurred in mitral valve disease, ischemic heart disease, congenital abnormalities and congestive cardiomyopathy, but not in the right ventricle of patients with myocarditis. The isoproterenol/calcium ratio correlated negatively with the age of the patient (P less than 0.001, n = 26, left ventricle). Multiple regression indicated that the maximum contraction amplitudes in either high isoproterenol or high calcium declined significantly with age only, but that both age and severity of disease contributed to the decrease in isoproterenol/calcium ratio. Time-to-peak tension in isoproterenol, as well as relaxation times in high calcium also decreased with the age of the patient. Analysis of variance showed that between-patient variation was significantly greater than between-cell for most of the parameters measured. Beta-adrenoceptor desensitisation may be detected in individual myocytes from failing hearts, and this relates more to the severity of disease and the age of the patient rather than the etiology of heart failure. A decline in absolute contractility of muscle cells with age was detected.

Cardiovascular and hormonal effects of calcitonin gene-related peptide in congestive heart failure

The effects of infusing human alpha-calcitonin gene-related peptide were studied in eight patients with congestive heart failure, five normal rabbits and five rabbits with adriamycin-induced cardiomyopathy. In patients with heart failure, calcitonin gene-related peptide caused a dose-dependent increase in cardiac output and decrease in pulmonary and systemic vascular resistance and pulmonary artery pressure. The systemic blood pressure and right atrial and pulmonary wedge pressures decreased only at the highest infusion rate (16 ng/kg per min). Heart rate remained unchanged. Plasma epinephrine increased (p less than 0.05), whereas aldosterone, atrial natriuretic peptide and prolactin concentrations decreased (p less than 0.05). Plasma norepinephrine, renin activity, cortisol and growth hormone concentrations remained unchanged. In both groups of rabbits, the drug decreased blood pressure and increased cardiac output and heart rate. There was a significant increase in renal blood flow (p less than 0.05). The peptide did not affect the contraction amplitude of human and rabbit ventricular myocytes. These findings suggest that calcitonin gene-related peptide is a vasodilator in the rabbit and humans with little direct effect on ventricular myocardium. This peptide may be useful in some forms of heart failure.

Reduced beta-agonist sensitivity in single atrial cells from failing human hearts

Human myocytes were isolated from right atrial appendage, and contractile responses to inotropic agents were studied. Responses to inotropic agents of cells isolated from patients with mild heart disease [New York Heart Association (NYHA) classes I and II] were compared with those of myocytes from rabbit atria. Maximally effective concentrations of calcium, forskolin, and isoproterenol increased contraction amplitude to a similar extent (11.9, 11.5, and 11.3% change in cell length, respectively), but histamine produced a smaller effect (7.1%). The maximum responses of rabbit atrial cells to calcium (18.5%) and isoproterenol (15.0%) were significantly greater than human. In human cells, the velocity of contraction or relaxation was accelerated more by isoproterenol (P less than 0.05) or forskolin (P less than 0.01) than by high calcium. Only relaxation velocity was increased by isoproterenol in rabbit cells (P less than 0.05). Rabbit myocytes contracted and relaxed 10-30% faster than human (P less than 0.05). Cells from the atria of patients with New York Heart Association (NYHA) heart failure class III or IV were less responsive to isoproterenol than those from class I or II (P less than 0.01). Omitting data from patients who had been taking calcium-channel blockers or beta-adrenoceptor agonist or antagonist drugs did not affect the conclusions. Analysis of variance revealed a significantly greater between-patient than within-patient variation (P less than 0.001), indicating that cells from the same patient have a tendency to respond in a similar way. Responses to high calcium did not differ among NYHA classes. The effect of forskolin was not reduced in NYHA class III, although there was a decreased response in cells from two patients in NYHA class IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Species dependence of contraction velocity in single isolated cardiac myocytes

Single myocytes were isolated from mouse, rat, guinea-pig, rabbit, sheep and human ventricle, and the amplitude and velocity of their unloaded contraction measured using a video camera and a system for measuring their length. Measurements were done at 32 degrees C in solutions containing either low calcium (1-1.3mM) or a concentration of calcium (usually 8mM) that produced a maximum amplitude of contraction. Unlike the cells of the majority of species, human cells could be successfully isolated only by using protease in addition to collagenase. To determine the effect of protease, guinea-pig cells were prepared with or without this enzyme. There was no significant difference in the characteristics of the cells prepared by either method. There was little species variation in the length of the cells or the length of resting sarcomeres. However, there were considerable species differences in the velocity of shortening and of relaxation. Myocytes from larger animals tended to contract and relax more slowly than those from smaller animals, although there was little systematic variation in the absolute amplitude of contraction. There was a significant correlation between the normalised contraction velocity of single cells and the average heart rate reported for that species. The trend for decreased relaxation velocity with lower heart rate did not reach statistical significance. Right ventricular cells from rat heart contracted more rapidly than those from the left ventricle, a finding similar to that reported for intact muscle strips. We conclude that species and left/right differences observed in the contraction velocity of whole muscle can be detected at the level of the single myocyte.

Assessment of regional myocardial perfusion with thallium imaging during transient left anterior descending coronary arterial occlusion during angioplasty

To define the jeopardized territory perfused through a single coronary arterial stenosis, thallium-201, 2 mCi, was injected into the pulmonary artery at the onset of the last of a series of percutaneous transluminal coronary angioplasty (PTCA) balloon inflations in 10 patients with single-vessel left anterior descending coronary artery disease. Imaging was begun immediately after PTCA. Arterial thallium activity peaked 30 seconds after injection and decreased to 34 +/- 6% (mean +/- standard error of the mean) of peak activity at the time of balloon deflation. Regional thallium activity during exercise vs PTCA was scored qualitatively and quantitatively. A computer quantification program was used that permitted automatic realignment and normalization of the 2 initial thallium images. Only mean quantitative posterior activity was lower (93 +/- 1% vs 86 +/- 2%, p less than 0.05) on exercise scans compared with PTCA scans. The other 5 segments showed no difference in mean scores. There were no qualitative differences in initial thallium distribution, nor were there qualitative or quantitative differences in the number of abnormal segments or severity of reduction in activity in the segment with the lowest activity. In conclusion, regional thallium myocardial distribution with a single severe stenoses with injection during peak exercise is similar to that after complete coronary occlusion.

Gastric operations and glucose homeostasis. II. glucagon and secretin

Alimentary hyperglycemia in patients who have undergone gastric operations may be due, in part, to altered intestinal signals for glucose disposition. We measured glucose, immunoreactive insulin (IRI) pancreatic glucagon (IRG), and glucagon-like immunoreactivity (GLI) after oral glucose in patients with prior antrectomy or vagotomy and pyloroplasty and in normal individuals. All subjects had normal assimilation coefficients for intravenous glucose, which suggests that the responsiveness of the pancreatic beta-cells had not been altered by the surgical procedures. The early hyperglycemic response to oral glucose and the associated elevation of plasma GLI were much greater and the IRI levels slightly higher in both experimental groups in comparison to normal subjects. A decrease in the level of IRG, albeit not statistically significant, was noted in all groups after the ingestion of glucose. In gastrectomy patients, secretin infusion during repeated oral glucose tolerance tests partially corrected the hyperglycemia and lowered plasma GLI and IRI levels. The responses of the vagotomy and pyloroplasty patients and of the normal subjects were not altered by secretin infusion. We conclude that the intolerance or oral glucose after gastric surgery may be related to elevated GLI levels, and that the beneficial effect of secretin may be due to its ability to decrease these levels.