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Vivek Rao

Publications and source records attributed to Vivek Rao.

At least 73 records · Page 4Linked to original sources
PubMed2002

Are stentless valves hemodynamically superior to stented valves? A prospective randomized trial.

BACKGROUND: Although stentless aortic bioprostheses are believed to offer improved outcomes, hemodynamic benefits remain unsubstantiated. METHODS: Fifty-three patients were randomized to receive the stented C-E pericardial valve (CE) and 46 patients the Toronto Stentless Porcine valve (SPV). Annuli were sized for the optimal insertion of both valve types, such that surgeons were required to commit to specific valve sizes before randomization. Echocardiographic measurements and functional status (Duke Activity Status Index) were assessed at 3 and 12 months postoperatively. RESULTS: Although cardiopulmonary bypass times (CE: 118.6+/-36.3 minutes; SPV: 148.5+/-30.9 minutes; p = 0.0001) and aortic cross-clamp times (CE: 95.4+/-28.6 minutes; SPV: 123.6+/-24.1 minutes; p = 0.0001) were significantly prolonged in the SPV group, perioperative morbidity and mortality was similar between groups. Neither valve offered a superior internal diameter for any given annular diameter (mean decrease in left ventricular outflow tract diameter after valvular implantation: SPV: 3.4+/-1.11 mm versus CE: 3.7+/-1.33 mm; p = 0.25). Although labeled mean valve size was significantly larger in the SPV group, the actual mean valve size based on internal valvular diameter was no different between groups (CE: 21.9+/-2.0 mm; SPV: 22.3+/-2.0 mm; p = 0.286). Although effective orifice areas increased, and mean and peak transvalvular gradients decreased in both groups over time, no differences were demonstrated between groups at 12 months. Similarly, although significant regression of left ventricular mass was accomplished in both groups over time, no differences were demonstrated between groups. Finally, Duke Activity Status Index scores of functional status improved in both groups over time; however, no differences were noted between groups at 12 months postoperatively. CONCLUSIONS: Although offering excellent outcomes, stentless valves did not demonstrate superior hemodynamic indices in comparison to stented valves up to 12 months after implantation.

Aged↗
PubMed2002

LVAD support in patients with bioprosthetic valves.

The presence of mechanical or bioprosthetic valves has traditionally excluded patients from mechanical circulatory support. However, several centers have now developed algorithms for the surgical management of native or prosthetic valve disease in patients requiring left ventricular assist device insertion. We report adverse events associated with bioprosthetic valves in the mitral and tricuspid positions in 2 patients who received long-term mechanical support. We recommend anticoagulation for all patients with prosthetic valves in the mitral or tricuspid position to avoid thromboembolism, inflow conduit occlusion, or valvular incompetence.

Aortic Valve↗
PubMed2002

Endothelin blockade potentiates endothelial protective effects of ACE inhibitors in saphenous veins.

BACKGROUND: Angiotensin II and endothelin-1 are potent endothelium-derived contracting factors. The effects of acute endothelin antagonism on endothelial function in saphenous vein from patients treated with and without angiotensin-converting enzyme inhibitors were compared. METHODS: Vascular segments of saphenous vein were obtained perioperatively from 14 patients on angiotensin-converting enzyme inhibitors and 29 controls. In vitro endothelium-dependent and -independent responses to acetylcholine and sodium nitroprusside were assessed by constructing isometric dose-response curves in precontracted rings in the presence and absence of bosentan (endothelinA/B receptor antagonist) and BQ-123 (endothelinA antagonist) using isolated organ baths. Percent maximum relaxation and sensitivity were compared between interventions. RESULTS: Endothelium-dependent relaxation to acetylcholine was augmented in the angiotensin-converting enzyme inhibitor-treated group (p < 0.005). Both specific and mixed endothelin receptor blockade improved acetylcholine-mediated relaxation in the angiotensin-converting enzyme inhibitor-treated and untreated groups (p < 0.02). The effects of these antagonists were endothelium specific as endothelium-independent responses to sodium nitroprusside remain unaltered. CONCLUSIONS: These data demonstrate that (1) chronic angiotensin-converting enzyme inhibition improves endothelial function in saphenous veins, and (2) this effect can be further augmented by acute endothelin blockade. These data suggest that antagonism of both angiotensin II and endothelin may be important in attenuating saphenous vein arteriosclerosis.

Acetylcholine↗
PubMed2002

Reoperative mitral valve replacement: importance of preservation of the subvalvular apparatus.

BACKGROUND: Preservation of the subvalvular apparatus has been demonstrated to be beneficial during first-time mitral valve replacement (MVR), but has not been fully examined in reoperative (redo) MVR. The purpose of this study was to analyze outcomes in a large cohort of redo MVR patients, focusing on the effect of subvalvular preservation on mortality. METHODS: We undertook a review of prospectively gathered data on patients undergoing MVR, with or without concomitant cardiac procedures, at our institution from 1990 to 1999. Predictors of mortality were determined by stepwise logistic regression. RESULTS: A total of 1,521 consecutive MVR patients were analyzed, of which, 513 (34%) had undergone one or more previous MV procedures. In-hospital mortality occurred in 6.9% of first-time MVR patients versus 9.0% in redo patients (p = 0.13). The number of prior MV operations ranged from one to five in redo MVR patients, with 115 patients (22% of redos) having two or more. In redo MVR patients, preservation of the native posterior subvalvular apparatus was performed in 103 patients (21%), whereas native anterior and posterior preservation was performed in 31 patients (6%). Gore-Tex neochordal construction was performed in 135 redo MVR patients (26%). Perioperative mortality occurred in 3.6% of redo MVR patients with a preserved subvalvular apparatus (native tissue and/or Gore-Tex reconstruction) versus 13.3% of redo patients without preservation (p < 0.001). Independent predictors of mortality in redo MVR patients were (in decreasing order of magnitude) failure to preserve the subvalvular apparatus, preoperative renal failure, previous stroke/transient ischemic attack, left ventricular dysfunction (left ventricular ejection fraction <40%), and urgent timing. CONCLUSIONS: Redo MVR can be performed with an acceptable risk of mortality. Although preservation of the subvalvular apparatus may increase operative complexity, we recommend subvalvular preservation in order to decrease the risk of early mortality.

Adult↗
PubMed2002

Should moderate acute rejection of a cardiac transplant graft be treated?

UNLABELLED: Histologically proven, moderate acute rejection after orthotopic heart transplantation (OHT) is commonly treated with intravenous steroids. This regimen may result in severe metabolic and infectious side-effects. The purpose of this study was to assess and compare outcomes in treated (T) versus not treated (N-T) biopsy proven 3A rejection episodes in cardiac transplant recipients. METHODS: A retrospective analysis was conducted to identify all biopsy proven 3A rejection episodes that occurred over the time period 1995-2000 in patients (patients) >or= 6 months after OHT (n=48 episodes in 35 patients). Of the 48 episodes, 19 were N-T and 29 were T. Decision to treat 3A rejection was based on time after transplant, haemodynamic and/or clinical compromise and left ventricular (LV) dysfunction measured by 2D echo. Most N-T episodes received an increase in background immunotherapy. RESULTS: Time from transplant to index 3A episode in N-T patients was 4.2 versus 2.7 yr for the T patients (p=0.06). There were no differences seen between T and N-T groups for the first and second post-3A biopsy results or LV function post-3A. Presence of coronary disease or death were not different between groups. Of the 29 patients with T episodes, no differences in outcomes (death, first and second post-3A biopsy score, coronary disease, myocardial infarction, or LV function) were seen based on use of treatment with intravenous versus oral steroid. CONCLUSION: In patients more than 6 month after OHT, there were no differences in outcomes (ongoing rejection or LV function) between N-T episodes of 3A rejection and T episodes. In T patients the use of oral steroids was equally as effective for treatment of 3A episodes as intravenous steroids.

Adolescent↗
PubMed2002

The insulin cardioplegia trial: myocardial protection for urgent coronary artery bypass grafting.

BACKGROUND: Small, nonrandomized clinical trials have demonstrated a beneficial effect of solutions containing insulin and glucose on the recovery of myocardial metabolism and ventricular function after cardioplegic arrest and reperfusion. However, no large, blinded, randomized study has yet determined the effects of insulin-enhanced cardioplegia on clinical outcomes after coronary artery bypass grafting. METHODS: The Insulin Cardioplegia Trial was designed to evaluate the clinical impact of insulin-enhanced cardioplegia on patients at high risk undergoing isolated coronary artery bypass grafting for unstable angina. A total of 1127 patients were randomly assigned at operation to receive cardioplegic solution supplemented with 10 IU/L insulin (n = 557) or placebo (n = 570). All personnel with direct patient contact were blinded to randomization group. RESULTS: Overall operative mortality was 2.2%, with no significant differences between groups. The prevalences of postoperative low output syndrome (insulin 10.4%, placebo 9.7%, P =.7) and enzymatic myocardial infarction (insulin 21.0%, placebo 18.8%, P =.3) were not different between groups. The primary composite outcome of low output syndrome and/or enzymatic myocardial infarction revealed no difference between groups (insulin 30.0%, placebo 26.3%, P =.2). CONCLUSIONS: Despite encouraging results from smaller, nonrandomized studies, the Insulin Cardioplegia Trial failed to demonstrate a clinical benefit of insulin-enhanced cardioplegic solution for patients undergoing high-risk isolated coronary artery bypass grafting.

Adult↗
PubMed2002

Novel cardioprotective effects of tetrahydrobiopterin after anoxia and reoxygenation: Identifying cellular targets for pharmacologic manipulation.

OBJECTIVES: Contemporary cardioprotective strategies to prevent perioperative ischemia-reperfusion injury have focused on the l-arginine nitric oxide pathway. Tetrahydrobiopterin is an absolute cofactor required for the enzyme nitric oxide synthase and is thus a critical determinant of nitric oxide production. We hypothesized that ischemia-reperfusion results in diminished levels of tetrahydrobiopterin, which might represent a key cellular defect underlying endothelial and myocyte dysfunction after ischemia-reperfusion. To this aim, we examined the effects of tetrahydrobiopterin supplementation in (1) an in vivo experimental model of global ischemia-reperfusion and (2) an in vitro human ventricular heart cell model of simulated ischemia-reperfusion. Measures of endothelial function, oxidant production, cell survival, and cardiac function were used to assess outcome. METHODS: In study 1 Wistar rats were divided into one of 2 groups (n = 10 per group). One group received tetrahydrobiopterin (25 mg x kg(-1) x d(-1) for 7 days), and the other group served as the control group. Hearts were subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion, and left ventricular developed pressure, left ventricular systolic pressure, and left ventricular end-diastolic pressure were determined by using the modified Langendorff technique. In study 2 we quantitated myocardial malondialdehyde, a marker of lipid peroxidation, in ventricular tissues from both groups of animals using butanol phase extraction and spectrophotometric analysis. In study 3 coronary vascular responses were determined in vascular segments of the left coronary artery in both groups of animals after ischemia-reperfusion. Endothelium-dependent and endothelium-independent vasodilatation to acetylcholine and sodium nitroprusside, respectively, were compared between groups. In study 4, using a human ventricular heart cell model of simulated ischemia-reperfusion, we studied the effects of tetrahydrobiopterin (20 micromol/L) on cellular injury (as assessed by means of trypan blue uptake). RESULTS: After ischemia-reperfusion, myocardial dysfunction was evidenced by a decrease in left ventricular developed pressure and an increase in left ventricular end-diastolic pressure (P =.01 compared with baseline). Hearts from tetrahydrobiopterin-treated rats exhibited protection against ischemia-reperfusion injury (left ventricular developed pressure: 74 +/- 4 vs control 42 +/- 8 mm Hg, P =.01; left ventricular end-diastolic pressure: 12 +/- 3 vs 34 +/- 7 mm Hg, P =.01). Furthermore, tetrahydrobiopterin treatment attenuated the rise in malondialdehyde levels after ischemia-reperfusion (P =.01). After reperfusion, coronary endothelial function to acetylcholine was attenuated (P =.003 vs sham-treated mice), whereas responses to sodium nitroprusside remained unchanged. Tetrahydrobiopterin-treated rats exhibited an improvement in acetylcholine-mediated vasorelaxation (P =.01 vs ischemia-reperfusion group). Cellular injury, as assessed by means of trypan blue uptake, was higher in human ventricular heart cells subjected to simulated ischemia-reperfusion; this effect was prevented with tetrahydrobiopterin treatment (P =.001). CONCLUSIONS: Supplemental tetrahydrobiopterin provides a novel cardioprotective effect on left ventricular function, endothelial-vascular reactivity, oxidative damage, and cardiomyocyte injury after ischemia-reperfusion injury and might represent an important cellular target for future operative myocardial protection strategies.

Adolescent↗
PubMed2002

Increased endothelin-1 production in diabetic patients after cardioplegic arrest and reperfusion impairs coronary vascular reactivity: reversal by means of endothelin antagonism.

OBJECTIVES: Evidence has accrued to suggest that diabetic patients face an increased risk of ischemic events and low output syndrome and might mount an inordinate response to ischemia and reperfusion. Because hyperglycemia is a potent stimulus for endothelin-1 production, we hypothesized that increased production, action, or both of endothelin-1 in diabetes might represent an important mediator of endothelial dysfunction in patients with that disease. To this aim, we compared the effects of cardioplegic arrest and reperfusion on coronary sinus effluent endothelin-1 levels and atrial arteriolar vascular responses in diabetic and case-matched nondiabetic patients undergoing coronary artery bypass grafting. METHODS: In study 1 coronary sinus effluent endothelin-1 levels were assessed at baseline and at 1 and 10 minutes after reperfusion in 13 diabetic and 12 nondiabetic patients matched for age, ejection fraction, Parsonnet score, and crossclamp time. In study 2 vascular responses of atrial arterioles subjected to perioperative ischemia-reperfusion were evaluated with videomicroscopy. Atrial microvessels (from appendages) were obtained before and after removal of the aortic crossclamp, and vascular responses to exogenously administered endothelin-1 (10(-10) mol/L) and substance P (10(-8) mol/L) were studied in the presence or absence of BQ-123, an endothelin A receptor antagonist. RESULTS: Diabetic patients elaborated more endothelin-1 at 1 and 10 minutes after reperfusion (P =.01). Endothelin-1-mediated vasoconstriction was similar in diabetic and nondiabetic atrial microvessels before cardioplegic arrest and cardiopulmonary bypass. After cardiopulmonary bypass and reperfusion, endothelin-1-mediated vasoconstriction was enhanced in both groups; however, this response was greater in microvessels from diabetic patients (P =.02). BQ-123, the endothelin A antagonist, attenuated the effects of bypass and reperfusion on endothelin-1-mediated vasoconstriction in both groups (P =.01). Substance P-mediated vasodilatation was similar in diabetic and nondiabetic atrial microvessels before bypass. After bypass and reperfusion, substance P-mediated vasodilatation was diminished in both groups; however, this response was more pronounced in the diabetic group (P =.003). BQ-123 coincubation restored substance P-mediated vasodilatation in both groups. CONCLUSIONS: We determined the following: (1) the coronary effluent release of endothelin-1 is higher in diabetic than in nondiabetic patients after cardiopulmonary bypass and reperfusion; (2) diabetic coronary microvessels respond to bypass and reperfusion with greater endothelin-1-mediated vasoconstriction and diminished nitric oxide-mediated vasodilatation; and (3) these effects are attenuated by endothelin antagonism. Endothelin-1 might be an important mediator of ischemia-reperfusion injury in patients with diabetes. Furthermore, use of endothelin receptor antagonists might be a novel strategy for improving the resistance of the diabetic heart to cardioplegic arrest and reperfusion.

Aged↗
PubMed2002

Hyperglycemia exaggerates ischemia-reperfusion-induced cardiomyocyte injury: reversal with endothelin antagonism.

OBJECTIVES: We have previously demonstrated an importance of endothelin-1 in diabetic patients undergoing bypass surgery. Recent evidence suggests that cardiomyocytes might also produce endothelin-1, which might directly impair myocyte contractility by increasing intracellular calcium levels. Because hyperglycemia is a potent stimulus of endothelin-1 production, we hypothesized that increased production, action, or both of endothelin-1 might be a mediator of direct cardiomyocyte injury in diabetes. Therefore we studied the effects of endothelin receptor blockers (BQ-123 and bosentan) on hyperglycemia-induced endothelin-1 production and cellular injury after ischemia-reperfusion. METHODS: Using a human ventricular heart cell model of simulated ischemia-reperfusion, we studied the effects of normoglycemia (5 mmol/L, 48 hours) and hyperglycemia (25 mmol/L, 48 hours) on cellular injury and endothelin-1 production. Furthermore, the effects of selective endothelin-A and mixed endothelin-A/B receptor antagonism (with BQ-123 and bosentan, respectively) were evaluated. RESULTS: Cellular injury, as assessed by means of trypan blue uptake, was higher in human ventricular heart cells subjected to hyperglycemia and simulated ischemia-reperfusion injury (P =.01); this effect was prevented with both BQ-123 and bosentan (P =.01). In addition, heart cells from the hyperglycemic group elaborated more endothelin-1 after ischemia-reperfusion (P =.02). CONCLUSIONS: Endothelin-1 production and cellular injury were greater in human ventricular heart cells subjected to hyperglycemic conditions and simulated ischemia-reperfusion. These effects are mediated by endothelin-A receptors because both BQ-123 and bosentan exerted similar degrees of protection. Endothelin receptor blockade is a novel strategy to improve the resistance of the diabetic heart to cardioplegic arrest and reperfusion.

Antihypertensive Agents↗
PubMed2002

L-arginine protects human heart cells from low-volume anoxia and reoxygenation.

Protective effects of L-arginine were evaluated in a human ventricular heart cell model of low-volume anoxia and reoxygenation independent of alternate cell types. Cell cultures were subjected to 90 min of low-volume anoxia and 30 min of reoxygenation. L-Arginine (0-5.0 mM) was administered during the preanoxic period or the reoxygenation phase. Nitric oxide (NO) production, NO synthase (NOS) activity, cGMP levels, and cellular injury were assessed. To evaluate the effects of the L-arginine on cell signaling, the effects of the NOS antagonist N(G)-nitro-L-arginine methyl ester, NO donor S-nitroso-N-acetyl-penicillamine, guanylate cyclase inhibitor methylene blue, cGMP analog 8-bromo-cGMP, and ATP-sensitive K+ channel antagonist glibenclamide were examined. Our data indicate that low-volume anoxia and reoxygenation increased NOS activity and facilitated the conversion of L-arginine to NO, which provided protection against cellular injury in a dose-dependent fashion. In addition, L-arginine cardioprotection was achieved by the activation of guanylate cyclase, leading to increased cGMP levels in human heart cells. This action involves a glibenclamide-sensitive, NO-cGMP-dependent pathway.

Arginine↗
PubMed2002

A simple method of creating LVAD outflow tract aortic anastomosis.

Left ventricular assist device (LVAD) implantation is frequently complicated by intraoperative and postoperative bleeding, particularly at the aortic anastomosis site. Many modifications of the anastomosis have been attempted. We describe a simple method to anastomose the LVAD outflow tract to the ascending aorta with minimal bleeding and a short anastomosis time.

Cardiac Surgical Procedures↗
PubMed2002

Donor management in cardiac transplantation.

The most important limitation in organ transplantation is donor availability. Canada is facing a serious situation with respect to organ donation rates and transplantation. The number of patients listed for heart transplant continues to increase while the number of available donors has plateaued. Several steps can be taken to address this growing mismatch. The proper identification and assessment of potential donors together with improvements in medical management may increase the donor pool. Additionally, the use of marginal donors and the development of new organ preservation techniques may lead to an increase in the number of potential heart transplants in Canada. This paper summarizes the identification, evaluation and management of heart transplant donors, and defines strategies to improve procurement activity in heart transplantation.

Brain Death↗
PubMedDate not supplied

The intricacies of cardiac sarcoidosis: a case report involving the coronary arteries and a review of the literature.

BACKGROUND: Primary cardiac sarcoidosis (CS) is rare, and concomitant involvement of the coronary arteries is rarer still. Successful diagnosis of this disease is difficult due to its nonspecific symptoms which mimic those of idiopathic dilated cardiomyopathy (IDCM). METHODS AND RESULTS: We describe a 47-year-old Caucasian male who underwent orthotopic heart transplant for presumed IDCM. Examination of the explanted heart revealed numerous nonnecrotizing granulomata throughout, similar granulomata in the walls of the large coronary arteries, and large areas of fibrosis. CONCLUSIONS: In cases of IDCM with symptoms of angina or acute coronary syndrome, the possibility of CS should be considered. Herein, we present this case and a review of the relevant literature.

Angina Pectoris↗
PubMedDate not supplied

Explantation of a mechanical assist device: assessment of myocardial recovery.

Reliable predictors of myocardial recovery post-mechanical assist device implantation are not well defined. We report the case of a 29-year-old woman with refractory congestive heart failure due to acute myocarditis of unknown etiology. The patient was supported with a HeartMate (Thoratec Corp., Woburn, MI) left ventricular assist device for 100 days showing improvement in clinical status. Hemodynamic monitoring, dobutamine stress echocardiography, and cardiopulmonary testing were performed to identify myocardial recovery. Improvements in myocardial reserve, hemodynamic parameters, and myocardial oxygen consumption were identified prior to explantation. The patient was successfully explanted. This case confirms that myocardial recovery is feasible with the use of a mechanical assist device. This article describes our current left ventricular assist device weaning protocol.

Adult↗
PubMedDate not supplied

Myocardial protection in reoperative coronary artery bypass grafting:.

Redo coronary artery bypass grafting (CABG) is associated with higher morbidity and mortality when compared to first-time CABG. Myocardial infarction and dysfunction contribute significantly to the increased risk of redo CABG. Results of reoperative coronary surgery have gradually improved, largely because of improvements in myocardial protection techniques. In the present review we will highlight the principles of myocardial protection in redo CABG patients with an emphasis on retrograde cardioplegia.

Coronary Artery Bypass↗
PubMedDate not supplied

Changing trends in mechanical circulatory assistance:.

BACKGROUND: The success of long-term implantable ventricular assist devices has led to their increased use in patients previously thought to be unsuitable for mechanical support. As a result, the demographic profile of patients presenting for LVAD support has changed over time. We reviewed our institutional experience to identify emerging risk factors and changing trends in patients who received the HeartMate VE LVAD. METHODS: The clinical records were reviewed of 131 consecutive LVAD recipients between 1996 and 2001. All perioperative data were collected prospectively and entered into an institutional database. All patients received a preoperative risk stratification score based upon published criteria. The cohort was arbitrarily divided into early (n = 45), mid (n = 45), and late groups (n = 41). RESULTS: Overall operative mortality was 25% with no difference between groups. The mean risk score increased significantly over time (early 3.5 +/- 0.4 vs. late 5.3 +/- 0.3, p < 0.05). The proportion of patients at high risk for mortality (score >5) was significantly higher in the late group (51% vs. 29%, p < 0.05). Although ventilation time and ICU stay was similar for all groups, hospital stay was longer in the late group (43 days vs. 23 days, p < 0.05). Mean duration of support fell from 90 to 59 days, but this failed to achieve statistical significance. Out-patient therapy decreased from 73% in the early group to 15% in the late group (p < 0.001). Multivariate analysis identified right heart failure (odds ratio 4.1, 95% CI 2-11) and risk score (OR 1.4, 95% CI 1.2-1.6) as independent predictors of death. CONCLUSIONS: Despite an increasingly high risk patient population, the mortality associated with LVAD therapy has remained constant. Duration of LVAD support has decreased with a trend toward transplantation before hospital discharge. These data continue to support the aggressive institution of mechanical assistance for acute or chronic heart failure.

Adult↗