Therapeutic potential of nesiritide (recombinant b-type natriuretic peptide) in the treatment of heart failure

This review outlines the chemical properties, pharmacology and clinical trials data which support the development of nesiritide (synthetic human B-type natriuretic peptide, or hBNP) as a therapeutic agent for patients with decompensated congestive heart failure. Nesiritide is a 32-amino acid peptide, structurally identical to endogenous hBNP. Clinical trials with single bolus, repeated boluses and sustained infusions of nesiritide have demonstrated prompt, significant and sustained reductions in pulmonary capillary wedge pressure and increases in cardiac output, consistent with a direct vasodilator effect. Nesiritide has a short half-life, approximately 18 min, which is not dependent upon renal function. It not associated with tachyphylaxis through 24 h of therapy. Nesiritide is not an inotrope, and its action is not dependent upon beta adrenergic receptors. The safety profile has been excellent; the major adverse effect is hypotension. The frequency of ventricular arrhythmia is not increased in patients treated with nesiritide. In our opinion, nesiritide has many attributes of an ideal first-line therapeutic agent for decompensated heart failure.

Drug treatment of patients with decompensated heart failure

Decompensated heart failure (HF) may be defined as sustained deterioration of at least one New York Heart Association functional class, usually with evidence of sodium retention. Episodes of decompensation are most commonly precipitated by sodium retention, often associated with medication noncompliance. Our therapeutic approach to hospitalized patients is based on the documented hemodynamic responses to vasodilator therapy, with redistribution of mitral regurgitant flow to forward cardiac output and decompression of the left atrium. Invasive hemodynamic monitoring is seldom required for the effective management of patients with HF and there are risks associated with pulmonary artery catheterization. The currently available parenteral vasoactive drugs for decompensated heart failure include: (i) vasodilators such as nesiritide, nitroprusside and nitroglycerin (glyceryl trinitrate); (ii) catecholamine inotropes, primarily dobutamine; and (iii) inodilators such as milrinone, a phosphodiesterase inhibitor. Vasodilators are most appropriate for those patients who are primarily volume-overloaded, but with adequate peripheral perfusion. In this class of agents, nesiritide (recombinant human B-type natriuretic peptide) offers advantages over currently available drugs. Nesiritide produces rapid and sustained decreases in right atrial and pulmonary capillary wedge pressures, with reduction in pulmonary and systemic vascular resistance and increases in cardiac index. The hemodynamic effects of nesiritide infusion were sustained over a duration of 1 week and the drug may be used without intensive monitoring in patients with decompensated HF. Treatment with dobutamine is indicated in patients in whom low cardiac output rather than elevated pulmonary pressure is the primary hemodynamic aberration. However, milrinone reduces left atrial congestion more effectively than dobutamine, and is well tolerated and effective when used in patients receiving beta-blockers. In-patient therapy for decompensated HF is a short term exercise for symptom relief and provides an opportunity to re-assess management in the continuum of care.

An update on nesiritide for treatment of decompensated heart failure

In the July 1999 issue of this publication, we described the chemical properties, pharmacology and clinical trials involving nesiritide as a therapeutic agent for patients with decompensated heart failure (Exp. Opin. Invest. Drugs) (1999) 8(7):1063--1072). At the time of publication, the US Food and Drug Administration reviewed the clinical experience with the compound and did not approve the drug for clinical use. More data were requested regarding safety issues, comparison with nitroglycerine, onset of effects, need for invasive haemodynamic monitoring and symptomatic improvement. The VMAC Study was designed to address these issues. A dosing regimen, 0.2 microgram/kg bolus followed by 0.01 microg/kg/min continuous infusion, was chosen to provide rapid onset of actions and haemodynamic improvement without a high incidence of symptomatic hypotension. Nesiritide was superior to iv. nitroglycerine in its haemodynamic effects, easier to administer without the need for dose titration and better tolerated overall. The drug could be administered safely without the need for invasive haemodynamic monitoring. Symptomatic hypotension occurred in 4% of patients. Beneficial haemodynamic effects correlated with symptomatic improvement in heart failure patients. Nesiritide appears to be an ideal first-line agent for treatment of patients with acutely decompensated heart failure.

Rate-responsive pacing improves exercise tolerance in heart transplant recipients: a pilot study

BACKGROUND

Chronotropic incompetence is one cause of diminished exercise capacity in heart transplant recipients. If reinnervation occurs, it often is late after transplantation and is not always accompanied by functional improvements in peak heart rate and appropriate tachycardia during exercise. To determine the efficacy of rate-responsive pacing on peak heart rate and exercise capacity, the authors studied eight male heart transplant recipients (age 57 +/- 12 years; 23 +/- 9 months after transplantation) that had either atrial or dual-chambered pacemakers.

METHODS

All subjects completed two maximal graded exercise tests (GXT) using the Naughton treadmill protocol. During the first GXT, pacemakers were programmed for bradycardia support only and without rate responsiveness (unpaced). After a 14-day regimen of beta blockade with metoprolol to nullify the influence of circulating catecholamines on heart rate, subjects performed the second GXT with pacemakers programmed to respond optimally in the rate-responsive mode (paced).

RESULTS

Peak heart rate (149 versus 129 bpm), peak oxygen uptake (18.9 versus 15.4 mL/kg/min), treadmill time to exhaustion (14.6 versus 12.4 min), and minute ventilation (76.7 versus 66.2 L/min) were significantly increased (P < or = 0.05) during the paced versus unpaced GXT.

CONCLUSIONS

The results of this study demonstrate that chronotropic support of the transplanted heart using a rate-responsive pacemaker, with activity-based sensors programmed for maximal sensitivity, improves both peak heart rate and exercise capacity in heart transplant recipients significantly more than circulating catecholamines alone.

High dose angiotensin-converting enzyme inhibition prevents fluid volume expansion in heart transplant recipients

OBJECTIVES

We sought to test the hypothesis that plasma volume (PV) expansion in heart transplant recipients (HTRs) is caused by failure to reflexively suppress the renin-angiotensin-aldosterone (RAA) axis.

BACKGROUND

Extracellular fluid volume expansion occurs in clinically stable HTRs who become hypertensive. We have previously demonstrated that the RAA axis is not reflexively suppressed by a hypervolemic stimulus in HTRs.

METHODS

Plasma volume and fluid regulatory hormones were measured in eight HTRs (57+/-6 years old) both before and after treatment with captopril (225 mg/day). Antihypertensive and diuretic agents were discontinued 10 days before. The HTRs were admitted to the Clinical Research Center (CRC), and, after three days of a constant diet containing 87 mEq/day of Na+, PV was measured by using the modified Evans blue dye dilution technique. After approximately four months (16+/-5 weeks), the same HTRs again discontinued all antihypertensive and diuretic agents; they were progressed to a captopril dose of 75 mg three times per day over 14 days, and the CRC protocol was repeated.

RESULTS

Captopril pharmacologically suppressed (p<0.05) supine rest levels of angiotensin II (-65%) and aldosterone (-75%). The reductions in vasopressin and atrial natriuretic peptide levels after captopril did not reach statistical significance. The PV, normalized for body weight (ml/kg), was significantly reduced by 12% when the HTRs received captopril.

CONCLUSIONS

Extracellular fluid volume is expanded (12%) in clinically stable HTRs who become hypertensive. Pharmacologic suppression of the RAA axis with high-dose captopril (225 mg/day) returned HTRs to a normovolemic state. These findings indicate that fluid retention is partly engendered by a failure to reflexively suppress the RAA axis when HTRs become hypervolemic.

Heart failure and sleep-related breathing disorders

Despite advances in medical and surgical therapy, heart failure (HF) remains a common and serious problem. An association between HF and sleep-related breathing disorders has been recognized since Cheyne's observations in 1818, but only recently have treatment options targeting sleep-related breathing disorders become available. This overview will consider the clinical features, pathophysiology, and treatment options of sleep-related breathing disorders in patients with HF.

Long-term hemodynamic responses to vasodilator therapy in patients with severe left ventricular dysfunction

Maximal oral vasodilator therapy resulted in long-term reduction of initially elevated pulmonary vascular resistance in 10 of 13 patients with severe heart failure who tolerated inotrope-supported uptitration of afterload reduction. Eleven patients were unable to tolerate vasodilator therapy and required inotropic support for successful cardiac transplantation.

Sustained hemodynamic effects of an infusion of nesiritide (human b-type natriuretic peptide) in heart failure: a randomized, double-blind, placebo-controlled clinical trial. Natrecor Study Group

OBJECTIVES

The goal of this study was to further define the role of nesiritide (human b-type natriuretic peptide) in the therapy of decompensated heart failure (HF) by assessing the hemodynamic effects of three doses (0.015, 0.03 and 0.06 microg/kg/min) administered by continuous intravenous (IV) infusion over 24 h as compared with placebo.

BACKGROUND

Previous studies have shown beneficial hemodynamic, neurohormonal and renal effects of bolus dose and 6-h infusion administration of nesiritide in HF patients. Longer term safety and efficacy have not been studied.

METHODS

This randomized, double-blind, placebo-controlled multicenter trial enrolled subjects with symptomatic HF and systolic dysfunction (left ventricular ejection fraction < or =35%). Central hemodynamics were assessed at baseline, during a 24-h IV infusion and for 4 h postinfusion.

RESULTS

One hundred three subjects with New York Heart Association class II (6%), III (61%) or IV (33%) HF were enrolled. Nesiritide produced significant reductions in pulmonary wedge pressure (27% to 39% decrease by 6 h), mean right atrial pressure and systemic vascular resistance, along with significant increases in cardiac index and stroke volume index, with no significant effect on heart rate. Beneficial effects were evident at 1 h and were sustained throughout the 24-h infusion.

CONCLUSIONS

The rapid and sustained beneficial hemodynamic effects of nesiritide observed in this study support its use as a first-line IV therapy for patients with symptomatic decompensated HF.

Aerobic exercise attenuates blood pressure reactivity to cold pressor test in normotensive, young adult African-American women

Exaggerated blood pressure reactivity to behavioral stress has been observed in the African-American population, and such a pressor response is believed to play a role in hypertension. Regular aerobic exercise has been shown to exert an anti-hypertensive effect, and this may alter the blood pressure hyperreactivity observed in African Americans. To test the hypothesis that aerobic exercise attenuates pressor reactivity in African Americans, we studied eight healthy aerobically-trained normotensive African-American females and five similar sedentary females. The stress stimuli consisted of the cold pressor test with the foot immersed in ice water for two minutes. The aerobic exercise training protocol consisted of six weeks of jogging at 60-70% of peak oxygen uptake (VO2peak), three days/week for 35 min/exercise session. Systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, heart rate, cardiac output, total peripheral resistance, and forearm blood flow were measured. Manifestation of a training effect was illustrated by a 24.1 +/- 0.2% increase in VO2peak (26.9 +/- 1.2 mL x kg(-1) min(-1) vs 35.4 +/- 1.6 mL x kg(-1) min(-1)) (P<.05). Within the exercise-trained group there was a 6.3 +/- .15% decrease in systolic pressure (129 +/- 4.6 mm Hg vs. 121 +/- 5.4 mm Hg) (P<.05), and a 5.0 +/- .05% decrement in mean arterial blood pressure (99 +/- 3.3 mm Hg vs 94 +/- 3.6 mm Hg) (P<.05) during the cold pressor test. Pressor reactivity to cold stress did not change in the untrained group. Measures of heart rate, cardiac output, total peripheral resistance, and forearm blood flow were unaltered during conditions of the cold pressor test. We conclude that aerobic exercise attenuates the blood pressure reactivity to behavioral stress in young, adult normotensive African-American females. A lifestyle change such as exercising may play a role in reducing the risk of hypertension in African-American women.

Significance of radiographic cardiomegaly in orthotopic heart transplant recipients

OBJECTIVE

The purpose of this study is to evaluate the clinical significance of radiographic cardiomegaly in orthotopic heart transplant recipients and to identify causative anatomic and physiologic parameters.

MATERIALS AND METHODS

We retrospectively compared the cardiothoracic ratio (CTR) measured using standard posteroanterior chest radiography with left ventricular end-diastolic diameter and left ventricular ejection fraction measured on two-dimensional echocardiography; right ventricular systolic pressure; and systolic, diastolic, and mean blood pressure measured at biopsy in 46 heart transplant recipients.

RESULTS

Twenty-eight (61%) of the 46 patients had radiographic cardiomegaly. When we compared heart transplant recipients who had a CTR greater than 0.5 with recipients who had a CTR less than or equal to 0.5, we found no significant difference between their respective left ventricular end-diastolic diameters, left ventricular ejection fractions, right ventricular systolic pressures, systolic blood pressures, or mean blood pressures. A statistically significant difference existed between the mean values of diastolic blood pressure for transplant recipients with and without radiographic cardiomegaly. We found no significant correlation between CTR and left ventricular end-diastolic diameter, left ventricular ejection fraction, systolic blood pressure, diastolic blood pressure, or mean blood pressure.

CONCLUSION

The statistically significant difference between the mean values of diastolic blood pressure of transplant recipients with and without radiographic cardiomegaly is clinically insignificant and unlikely to account for the finding of radiographic cardiomegaly. We conclude that radiographic cardiomegaly, which occurs frequently in heart transplant recipients, does not correlate with anatomic or physiologic parameters obtained under the same conditions. Radiographic cardiomegaly in heart transplant recipients does not connote allograft dysfunction or heart failure.

Cardiac output responses during exercise in volume-expanded heart transplant recipients

The mechanisms responsible for immediate adjustments in cardiac output at onset of exercise, in the absence of neural drive, are not well defined in heart transplant (HT) recipients. Seven male HT recipients (mean +/- SD 57 +/- 6 years) and 7 age-matched sedentary normal control subjects (mean age 57 +/- 5 years) performed constant load cycle exercise at 40% of peak power output (Watts). Cardiac output and plasma norepinephrine were determined at rest and every 30 seconds during the first 5 minutes of exercise and at minutes 6, 8, and 10. All subjects were admitted to the General Clinical Research Center for determination of plasma volume. After 3 days of equilibration to a controlled and standardized diet, plasma volume was measured using a modified Evans Blue Dye (T-1824) dilution technique. Heart rate at rest was higher in the HT group (105 +/- 12 vs 74 +/- 6 beats/min), but during submaximum exercise, heart rates in the control group increased more rapidly (p < or = 0.05) and to a greater magnitude (54 +/- 7% vs 17 +/- 4% above rest). Stroke volume at rest was lower in HT recipients (45 +/- 4 vs 68 +/- 9 ml) but was significantly augmented immediately after onset of exercise (30 seconds) and the relative increase was greater than controls at peak exercise (61% vs 38% greater than baseline). Cardiac output at rest was within the normal range in both groups (4.58 +/- 0.27 vs 4.94 +/- 0.40 L/min). Relative increases in cardiac output were similar (p > or = 0.05) for the HT (106 +/- 12%) and control groups (97 +/- 10%). Plasma norepinephrine did not become significantly greater than resting values until approximately 4 minutes after onset of exercise in both groups. Blood volume, normalized for body weight, was 12% greater in the HT group. Thus, HT recipients with expanded blood volume (12%) augment stroke volume immediately after the onset of exercise. Plasma norepinephrine levels contribute negligibly to the rapid adjustment in cardiac output. Rather, we speculate that abrupt on-transit increases in stroke volume are due to augmented venous return, secondary to expanded blood volume.

Risk of death or incapacitation after heart transplantation, with particular reference to pilots

Pilots who have received a heart transplant may subsequently want to resume flying. This study was undertaken to determine whether a group of heart transplant recipients who had a particularly low risk of sudden unexpected death could be identified from clinical data. An event, "rapid-onset death," was defined incorporating a number of possible causes of death that could result in a heart transplant recipient-pilot losing control of an airplane. The survival of 3676 patients undergoing a first heart transplantation was 85% and 73% at 1 and 5 years, respectively, the hazard function having a high early phase of risk. When time zero was moved to the beginning of the second year after transplantation, the freedom from "rapid-onset death" at posttransplantation year 2 and posttransplantation year 5 was 96.8% and 88%, respectively. For patients who had both a "normal" coronary angiogram and no episodes of acute heart rejection during the first year transplantation, the probability of "rapid onset death" during the second posttransplantation year was 1.4%, and given the same circumstances, during the third posttransplantation year the risk of "rapid-onset death" was 1.6%. This information is potentially useful to the Federal Aviation Administration for policy decisions regarding this issue.

Resistance exercise prevents glucocorticoid-induced myopathy in heart transplant recipients

PURPOSE

To determine the effect of resistance exercise training (ET) on glucocorticoid-induced myopathy in heart transplant recipients (HTR), 14 male HTR were randomly assigned to a ET group that trained for 6 months (54 +/- 3 yr old; mean +/- SD) or a control group (51 +/- 8 yr old; mean +/- SD).

METHODS

Fat mass, fat-free mass, and total body mass were measured by dual-energy x-ray absorptiometry before and 2 months after transplantation (Tx), and after 3 and 6 months of ET or control period. The exercise regimen consisted of lumbar extension (MedX) performed 1 d.wk-1 and variable resistance exercises (Nautilus) performed 2 d.wk-1. PreTx body composition did not differ between groups.

RESULTS

At 2 months after Tx, fat-free mass was significantly decreased below baseline in both control (-3.4 +/- 2.1%) and ET groups (-4.3 +/- 2.4%). Fat mass was significantly increased at 2 months after Tx in both the control (+8.3 +/- 2.8%) and ET groups (+7.3 +/- 4.0%). Six months of ET restored fat-free mass to levels 3.9 +/- 2.1% greater (P < or = 0.05) than before Tx. Fat-free mass of the control group decreased progressively to levels that were 7 +/- 4.4% lower than preTx values (P < or = 0.05). Both groups increased knee extension, chest press, and lumbar extensor strength, but improvements in the ET group were four- to six-fold greater (P < or = 0.05).

CONCLUSION

Our results demonstrate that glucocorticoid-induced changes in body composition in HTR occur early after Tx. However, 6 months of specific ET restores fat-free mass to levels greater than before Tx and dramatically increases skeletal muscle strength. Resistance exercise, as part of a strategy to prevent steroid-induced myopathy, appears to be safe and should be initiated early after heart Tx.

Clinical improvement after atrioventricular nodal ablation for atrial fibrillation does not correlate with improved ejection fraction

A retrospective review of 15 patients with atrial fibrillation and class III to IV congestive heart failure who underwent atrioventricular nodal ablation demonstrated a marked improvement in their functional abilities. This improvement, however, could not be explained by the improvement in ejection fraction alone.

Permanent atrial pacing in cardiac transplant patients

Thirteen out of 223 consecutive cardiac transplant patients required permanent pacemaker implantation; 11 for sinus node dysfunction and 2 for complete AV block. Patients with sinus node dysfunction were considered for AAIR mode pacemakers if they had intact AV conduction defined as a Wenckebach point of > 120 beats/min. Ten of 11 patients with sinus node dysfunction had a single atrial lead placed. Atrial lead placement was most easily accomplished with a straight, active fixation lead and the use of manually curved stylets to find an optimal position in the donor atrium, although active fixation leads with a preformed atrial J were used as well. Two leads dislodged requiring revision. In contrast, only 1 of 250 atrial leads implanted in nontransplanted hearts dislodged (P < 0.0001). Transvenous endomyocardial biopsies have not caused atrial lead dislodgment. Most transplant recipients requiring permanent pacing have intact AV nodal function and require only atrial pacing. Atrial lead dislodgment requiring lead revision occurs more frequently in heart transplant recipients than in native hearts. Use of a straight active fixation lead with a manually formed curve in the stylet is useful in order to find the optimal position for pacing.

Heart transplant rejection with hemodynamic compromise: a multiinstitutional study of the role of endomyocardial cellular infiltrate. Cardiac Transplant Research Database

BACKGROUND

The natural history of patients experiencing hemodynamic compromise with rejection has been incompletely characterized. This multiinstitutional study examined the outcome of such episodes, particularly with regard to the extent of cellular infiltrate on the index endomyocardial biopsy.

METHODS

From January 1, 1990, through June 30, 1994, 3367 patients in the Cardiac Transplant Research Database experienced 4137 episodes of rejection. Severe hemodynamic compromise occurred in approximately 5% of the rejection episodes, and this proportion remained relatively constant over time.

RESULTS

Recipient risk factors for rejection with severe hemodynamic compromise included black race, female recipient sex, and diabetes. The 3-month actuarial survival rate was 60% after rejection with severe hemodynamic compromise versus 95% after rejection with no or mild compromise. Low initial biopsy score conferred a higher early survival, but a lower survival at 2 years after rejection with severe hemodynamic compromise. Among patients who survive an initial rejection episode with severe hemodynamic compromise, survival at 2 years after an episode was 46% among those who had a low initial biopsy score versus 84% with a high biopsy score.

CONCLUSIONS

Rejection with hemodynamic compromise, although rare, represents a major complication of heart transplantation with a poor long-term outcome. Survivors of hemodynamically compromising rejection episodes associated with low biopsy scores in the International Society for Heart and Lung Transplantation grading system have a significantly worse long-term outcome than survivors of episodes associated with high scores. These findings suggest that immunologic mechanisms other than lymphocytic infiltration of the cardiac allograft are important and distinct causes of allograft dysfunction.

QT dispersion is a marker for life-threatening ventricular arrhythmias after atrioventricular nodal ablation using radiofrequency energy

QT dispersion has been cited as a measure of nonuniform myocardial repolarization and a predictor of sudden cardiac death. We describe 38 patients who underwent atrioventricular nodal ablation, 3 of whom had an increase in measured QT dispersion and experienced potentially fatal, pulseless, polymorphic ventricular tachycardia after the procedure.

Dobutamine echocardiography for prediction of ischemic events in heart transplant recipients

The purpose of this study was to assess the use of dobutamine stress echocardiography in predicting cardiac events in heart transplant recipients. Dobutamine echocardiography was performed in 63 consecutive heart transplant recipients, 52 males and 11 females ranging in age from 12 to 77 years (mean 54), undergoing routine yearly evaluation. Twenty-one patients had abnormal wall motion at baseline or during dobutamine infusion. Over a mean follow-up of 8 months (range 4 to 14), there were six major cardiac events: five occurred among patients with abnormal echocardiography study results; only one event occurred in a patient with a normal echocardiography result. These data suggest that normal wall motion during dobutamine echocardiography identifies a subset of heart transplant recipients at low risk for development of cardiac events, whereas an abnormal study result serves as an important predictor of subsequent cardiac events.

Resistance exercise training restores bone mineral density in heart transplant recipients

OBJECTIVES

This was a prospective, randomized, controlled study designed to determine the effect of resistance exercise training on bone metabolism in heart transplant recipients.

BACKGROUND

Osteoporosis frequently complicates heart transplantation. No preventative strategy is generally accepted for glucocorticoid-induced bone loss.

METHODS

Sixteen male heart transplant recipients were randomly assigned to a resistance exercise group that trained for 6 months (mean [+/- SD] age 56 +/- 6 years) or a control group (mean age 52 +/- 10 years) that did not perform resistance exercise. Bone mineral density (BMD) of the total body, femur neck and lumbar spine (L2 to L3) was measured by dual-energy X-ray absorptiometry before and 2 months after transplantation and after 3 and 6 months of resistance exercise or a control period. The exercise regimen consisted of lumbar extension exercise (MedX) performed 1 day/week and variable resistance exercises (Nautilus) performed 2 days/week. Each exercise consisted of one set of 10 to 15 repetitions performed to volitional fatigue.

RESULTS

Pretransplantation baseline values for regional BMD did not differ in the control and training groups. Bone mineral density of the total body, femur neck and lumbar vertebra (L2 to L3) were significantly decreased below baseline at 2 months after transplantation in both the control (-3.3 +/- 1.3%, -4.5 +/- 2.8%, -12.7 +/- 3.2%, -14.8 +/- 3.1%, respectively). Six months of resistance exercise restored BMD of the whole body, femur neck and lumbar vertebra to within 1%, 1.9% and 3.6% of pretransplantation levels, respectively. Bone mineral density of the control group remained unchanged from the 2-month posttransplantation levels.

CONCLUSIONS

Within 2 months after heart transplantation, approximately 3% of whole-body BMD is lost, mostly due to decreases in trabecular bone (-12% to -15% of lumbar vertebra). Six months of resistance exercise, consisting of low back exercise that isolates the lumbar spine and a regimen of variable resistance exercises, restores BMD toward pretransplantation levels. Our results suggest that resistance exercise is osteogenic and should be initiated early after heart transplantation.

Fluid homeostasis after heart transplantation: the role of cardiac denervation

BACKGROUND

Orthotopic heart transplantation may interrupt key neural and humoral homeostatic mechanisms that normally adjust Na+ and fluid excretion to changes in intake. Such an interruption could lead to plasma volume expansion.

METHODS

We measured plasma volume and fluid regulatory hormones under standardized conditions in 11 heart transplant recipients (58 +/- 7 years old; mean +/- standard deviation) 21 +/- 4 months after transplantation, in 6 liver transplant recipients (51 +/- 6 years old) 13 +/- 8 months after transplantation (cyclosporine control group), and in 7 normal healthy control subjects (61 +/- 9 years old). Administration of all diuretics and antihypertensive drugs was discontinued before the study. After 3 days during which subjects ate a constant diet containing 87 mEq of Na+ per 24 hours, plasma volume was measured by a modified Evans blue dye (T-1824) dilution technique. Renal creatinine clearance was measured and blood samples were drawn for determination of plasma levels of vasopressin, angiotensin II, aldosterone, atrial natriuretic peptide, and plasma renin activity.

RESULTS

Supine resting plasma renin activity, angiotensin II, and aldosterone (renin-angiotensin-aldosterone axis) and vasopressin levels were not different among the control, heart transplant, and liver transplant groups. However, there was a trend toward elevated angiotensin II (p < or = 0.08) and aldosterone (p < or = 0.08) levels in the heart transplant recipients. Atrial natriuretic peptide levels were significantly elevated two to threefold in the heart transplant recipients when compared with those in the two control groups. Blood volume, normalized for body weight (milliliters per kilogram), was significantly greater (14%) in the heart transplant recipients when compared with that in liver transplant recipients and normal healthy control subjects. Blood volume values did not differ (p > or = 0.05) between the two control groups.

CONCLUSIONS

Extracellular fluid volume expansion (+14%) occurs in clinically stable heart transplant recipients who become hypertensive. Although hyperactivity of the renin-angiotensin-aldosterone axis is not apparent during supine resting conditions, our data suggest that the renin-angiotensin-aldosterone system is not responsive to a hypervolemic stimulus and this is likely a consequence of chronic cardiac deafferentation. Thus, poor adaptation of the renin-angiotensin-aldosterone system to fluid retention may be partly responsible for the incidence and severity of posttransplantation hypertension in some heart transplant recipients.

Aortic valve endocarditis in an acutely rejecting orthotopic heart transplant recipient

Infective endocarditis is an infrequent but serious complication in heart transplant recipients. We report successful treatment for this serious complication.

Bradycardia after heart transplantation: reversal with theophylline

OBJECTIVES

We attempted to demonstrate that theophylline, an adenosine receptor antagonist, can reverse bradyarrhythmias after orthotopic heart transplantation.

BACKGROUND

Sinus node dysfunction, primarily sinus bradycardia, frequently occurs after orthotopic heart transplantation and may lead to permanent pacemaker implantation. Endogenous adenosine has been implicated as a cause of such posttransplantation bradyarrhythmia.

METHODS

Twenty-nine transplant recipients (group 1) were given theophylline after bradyarrhythmias developed after transplantation. Data in these patients were compared with those in a control group of 18 patients without bradyarrhythmias (group 2) who were not given theophylline.

RESULTS

The mean heart rate in group 1 increased from 62 +/- 7 to 89 +/- 10 beats/min after administration of theophylline (p < 0.0001); the mean heart rate in group 2 was 88 +/- 12 beats/min. Patients in group 1 required more days of temporary atrial pacing (3.5 +/- 1 vs. 1.5 +/- 3, p < 0.04) before the administration of theophylline than did patients in group 2. The length of hospital stay after transplantation did not differ significantly between groups 1 and 2 (17 +/- 7.5 vs. 20 +/- 16 days, p = NS). Age, gender, underlying disease, preoperative use of amiodarone, graft ischemia time or the incidence of moderate to severe rejection were not different between patient groups.

CONCLUSIONS

The use of theophylline for posttransplantation bradyarrhythmias increased heart rate and facilitated the withdrawal of chronotropic support. We conclude that theophylline offers effective and specific therapy for heart transplant patients with early bradyarrhythmias, reducing the need for implantation of a permanent pacemaker.

Experimental and clinical allogeneic heart transplant rejection: correlations between histology and immune reactivity detected by cytokine messenger RNA

BACKGROUND

Cytokines produced by host cells infiltrating allogeneic transplants are critical determinants of graft rejection but information on cytokine production during graft rejection remains limited. No reported study on cytokine profiles has compared experimental allograft rejection induced by withdrawal of cyclosporine with clinical transplant rejection that occurs in the presence of therapeutic levels of cyclosporine.

METHODS

Functional activities of allograft-infiltrating host cells in sequential endomyocardial biopsies obtained before, during, and after acute heart transplant rejection were determined with the use of the reverse transcriptase-polymerase chain reaction to detect cytokine messenger RNA. These results were correlated with histologic findings in both an experimental canine model of heart transplant and rejection and in clinical human heart transplant recipients.

RESULTS

When experimental rejection was induced by withdrawal of immunosuppression, rejection was characterized by the presence of mRNA encoding CD4, CD8, interleukin-2 (but not interleukin-4), interleukin-2 receptor, and tumor necrosis factor-beta. These findings are consistent with a classic T-helper, T-cytotoxic cell-mediated response. However, the cytokine profile of human, clinical heart transplant rejection occurring in the presence of therapeutic levels of immunosuppression differed strikingly. In clinical rejection in human beings, histologic evidence of rejection was not associated with detectable interleukin-2 or interleukin-2 receptor mRNA.

CONCLUSIONS

Human, clinical heart rejection can occur in the absence of locally produced interleukin-2; the degree of immunosuppression achieved with cyclosporine A may explain the different results obtained in the canine withdrawal model versus human clinical allograft rejection.

Effectiveness and safety of diltiazem or lisinopril in treatment of hypertension after heart transplantation. Results of a prospective, randomized multicenter trail

OBJECTIVES

The purpose of this study was to determine the effectiveness and safety of diltiazem or lisinopril for treatment of hypertension after heart transplantation.

BACKGROUND

Systemic hypertension is common after heart transplantation, and to date there are no randomized, prospective multicenter treatment trials.

METHODS

Members of the Cardiac Transplant Research Database Group developed and implemented a prospective, randomized multicenter trial of the effectiveness and safety of diltiazem or lisinopril in the treatment of hypertension in cyclosporine-treated patients after heart transplantation.

RESULTS

One hundred sixteen patients with hypertension (blood pressure > or = 140/90 mm Hg) after heart transplantation were randomized for > or = 3 months of treatment. Of 55 diltiazem-treated patients, 21 (38%) were responders (diastolic blood pressure < 90 mm Hg), 23 (42%) were nonresponders (diastolic blood pressure > or = 90 mm Hg), and 11 (20%) were withdrawn from the study. Of 61 lisinopril-treated patients, 28 (46%) were responders, 22 (36%) were nonresponders, and 11 (18%) were withdrawn. There was no difference in baseline characteristics or percent responders between the two groups. Systolic pressure decreased from 157 +/- 2.3 to 130 +/- 2.0 mm Hg (mean +/- 1 SEM) in the diltiazem-treated responders and from 153 +/- 2.1 to 127 +/- 2.7 mm Hg in the lisinopril-treated responders (p < 0.0001). Diastolic pressure decreased from 100 +/- 0.9 to 85 +/- 1.6 mm Hg in the diltiazem-treated responders and from 100 +/- 1.0 to 84 +/- 2.0 mm Hg in the lisinopril-treated responders (p < 0.0001). There were a total of 35 reported adverse events, 22 of which led to withdrawal of the patient from the study. All drug-related side effects were considered minor and resolved with discontinuation of the drug.

CONCLUSIONS

These results indicate that both diltiazem and lisinopril are safe for treatment of hypertension after heart transplantation, although titrated monotherapy with either drug controlled the condition in < 50% of patients.

Evaluation of heart failure patients: objective parameters to assess functional capacity

Measures of disease severity used in the evaluation of patients with heart failure include survival data, the New York Heart Association classification, ejection fraction, functional assessments, exercise protocols, rest and exercise hemodynamic data, and biochemical parameters including catecholamine levels and serum sodium. Clinicians must integrate these multiple variables into an overall assessment. An overview of the clinical application of these techniques in the evaluation and treatment of patients with heart failure is presented.

Clinical importance of viability assessment in chronic ischemic heart failure

BACKGROUND AND HYPOTHESIS

Revascularization has provided an effective treatment of depressed left ventricular function in patients with chronically ischemic or "viable" myocardium. Assessment of viable myocardium can be achieved by several noninvasive techniques including dobutamine stress echo or radionuclides such as flurodeoxyglucose (F18DG). F18DG uptake studies are based on the assumption that enhanced glucose uptake in areas of diminished blood flow provides evidence of viable myocardium. To determine the clinical utility of viability assessment in the management of chronic ischemic left ventricular dysfunction, we reviewed the findings and short-term treatment of a series of patients referred for heart failure evaluation who had subsequent F18DG uptake scans.

METHODS

We retrospectively reviewed 59 consecutive F18DG viability studies in a series of patients who had documented coronary artery disease and depressed left ventricular function. Single photon emission computerized tomography (SPECT) with F18DG was performed in the patients and these images were compared to SPECT images of resting myocardial perfusion using thallium, sestamibi, or teboroxime. Clinical decisions based on the results of these scans were obtained from chart review. Thirty-day mortality was determined from chart review or contact with the patient's physician. The patients were divided into those without and with F18DG uptake consistent with viable ischemic myocardium. Further analysis included subgroups of patients who were advised to undergo transplantation, revascularization, or to continue medical therapy.

RESULTS

Of 34 patients referred for cardiac transplantation, 18 had viable myocardium and 13 underwent revascularization. In the entire study group, 34 of 59 (58%) had evidence of viable myocardium and 29 had subsequent revascularization procedures. Thirty-day survival for all revascularization patients was 86%.

CONCLUSION

Assessment of myocardial viability with F18DG SPECT imaging in patients with ischemic left ventricular dysfunction led to a clinical decision for revascularization in approximately half the patients with severe coronary disease and left ventricular dysfunction who were evaluated for myocardial viability in our institution.

Prolonged survival of a patient with left ventricular pseudoaneurysm following myocardial infarction and mitral valve replacement

We present the case of a patient with left ventricular pseudoaneurysm following acute myocardial infarction. Survival for 2 years following diagnosis, despite the large size of the aneurysm, and subsequent management with cardiac transplantation represent unusual and interesting aspects of this complication of myocardial infarction.

Breakdown of blood pressure and body fluid homeostasis in heart transplant recipients

OBJECTIVES

This study was designed to investigate disturbances in arterial blood pressure and body fluid homeostasis in stable heart transplant recipients.

BACKGROUND

Hypertension and fluid retention frequently complicate heart transplantation.

METHODS

Blood pressure, renal and endocrine responses to acute volume expansion were compared in 10 heart transplant recipients (57 +/- 9 years old [mean +/- SD]) 20 +/- 5 months after transplantation, 6 liver transplant recipients receiving similar doses of cyclosporine (cyclosporine control group) and 7 normal volunteers (normal control subjects). After 3 days of a constant diet containing 87 mEq/24 h of sodium, 0.154 mol/liter saline was infused at 8 ml/kg per h for 4 h. Blood pressure and plasma vasopressin, angiotensin II, aldosterone, atrial natiuretic peptide and renin activity levels were determined before and at 30, 60, 120 and 240 min during the infusion. Urine was collected at 2 and 4 h. Blood pressure, fluid balance hormones and renal function were monitored for 48 h after the infusion.

RESULTS

Blood pressure did not change in the two control groups but increased in the heart transplant recipients (+15 +/- 8/8 +/- 5 mm Hg) and remained elevated for 48 h (p < or = 0.05). Urine flow and urinary sodium excretion increased abruptly in the control groups sufficient to account for elimination of 86 +/- 9% of the sodium load by 48 h; the increases were blunted (p < or = 0.05) and delayed in the heart transplant recipients, resulting in elimination of only 51 +/- 13% of the sodium load. Saline infusion suppressed vasopressin, renin activity, angiotensin II and aldosterone in the two control groups (p < or = 0.05) but not in the heart transplant recipients. Heart transplant recipients had elevated atrial natriuretic peptide levels at baseline (p < or = 0.05), but relative increases during the infusion were similar to those in both control groups.

CONCLUSIONS

Blood pressure in heart transplant recipients is salt sensitive. These patients have a blunted diuretic and natriuretic response to volume expansion that may be mediated by a failure to reflexly suppress fluid regulatory hormones. These defects in blood pressure and fluid homeostasis were not seen in liver transplant recipients receiving cyclosporine and therefore cannot be attributed to cyclosporine alone. Abnormal cardiorenal neuroendocrine reflexes, secondary to cardiac denervation, may contribute to salt-sensitive hypertension and fluid retention in heart transplant recipients.

Risk factors for late recurrent rejection after heart transplantation: a multiinstitutional, multivariable analysis. Cardiac Transplant Research Database Group

BACKGROUND

Previous studies of allograft rejection have focused on early episodes and risk factors from pretransplant variables.

METHODS

This multiinstitutional study compared early (< 1 year) and late (> 1 year) rejection episodes and risk factors for recurrent rejection from variables both before and after transplantation among 1251 patients who underwent primary heart transplantation and available follow-up of greater than 1 year.

RESULTS

There were a total of 1882 rejection episodes over a mean follow-up of 26 +/- 0.3 months. The hazard function (instantaneous risk per patient per month) peaked at 1 month followed by a low constant risk of rejection after 12 months. By multivariable analysis, the most dominant risk factors for recurrent rejection during the first posttransplantation year were a shorter time interval since transplantation and a shorter time since a previous rejection episode. Other factors included young age, female gender, female donor, positive cytomegalovirus serology, prior infections, and OKT3 induction. In contrast, after the first year, the dominant risk factors for rejection were a greater number of rejections during the first year and the presence of prior cytomegalovirus infections.

CONCLUSIONS

These data show a striking time dependency for rejection episodes among heart transplant recipients. Factors that increase risk for rejection in the first year differ from risk factors for rejection in subsequent years. These data suggest that it may be possible to tailor rejection surveillance protocols and immunosuppression intensity, according to specific patient and time-related risk factors.

Exercise training in patients with congestive heart failure. How to achieve benefits safely

Inactivity adds to the decline of patients with congestive heart failure (CHF). However, in prescribing exercise in these patients, three principles must be understood: ejection fraction does not predict functional capacity, exercise can bring marked peripheral improvement without changing ejection fraction or hemodynamics, and benefits accrue slowly. The authors review the mechanisms of exercise intolerance in CHF and the factors to keep in mind when designing an exercise program.

Transplantation and the problems afterward including coronary vasculopathy

The clinical success of cardiac transplantation requires clinical cardiologists to become familiar with care of the post-transplant patient. This review emphasizes five major post-transplant problems: (1) infection/immunosuppression, (2) metabolic problems, (3) post-transplant hypertension, (4) exercise intolerance, and (5) graft coronary disease. The evolution of these problems after transplantation is emphasized, so that clinical cardiologists and internists sharing the management of these patients can develop a context in which to work.

Infection after heart transplantation: a multiinstitutional study. Cardiac Transplant Research Database Group

The incidence, causes, and impact of acute infection were analyzed among 814 consecutive patients from 24 institutions undergoing primary heart transplantation between January 1, 1990, and June 30, 1991, with mean follow-up of 8.2 months (range 0 to 18 months). Sixty-nine percent of the patients had no infections during the follow-up, whereas 31% of patients had one or more infection episodes. The cumulative incidence of infections per patient was 0.41 at 3 months, 0.55 at 6 months, and 0.62 at 12 months after transplantation. Bacterial and viral infections were most common (47% and 41% of infections), with fungi and protozoa accounting for 12%. Overall mortality per infection was 13%, but mortality with fungal infections was higher (36%, p < 0.0001). The most common organ infected was the lung, with a mortality of 23%. The probability of infection by 12 months was higher when OKT3 or antithymocyte globulin induction therapy was used (41% versus 35%, p = 0.01). The single most frequent infecting organism was cytomegalovirus, accounting for 26% of all infections. The probability of cytomegalovirus infection by 12 months was increased with a cytomegalovirus-positive donor and cytomegalovirus-negative recipient (27% versus 15% in all others, p < 0.0001) and with the use of OKT3 or antithymocyte globulin induction therapy (19% versus 12% without induction therapy, p = 0.07). Infection remains the leading cause of death after heart transplantation. The hazard function of likelihood of developing each type of infection at various times after transplantation, as well as response to therapy, are discussed.

Exercise-induced hypoxemia in heart transplant recipients

OBJECTIVES

The purpose of this study was to determine whether heart transplantation has an adverse effect on pulmonary diffusion and to investigate the potentially deleterious effects of impaired pulmonary diffusion on arterial blood gas dynamics during exercise in heart transplant recipients.

BACKGROUND

Abnormal pulmonary diffusing capacity is reported in patients after orthotopic heart transplantation. Abnormal diffusion may be caused by cyclosporine or by the persistence of preexisting conditions known to adversely affect diffusion, such as congestive heart failure and chronic obstructive pulmonary disease.

METHODS

Eleven patients (mean age 50 +/- 14 years) performed pulmonary function tests 3 +/- 1 months before and 18 +/- 12 (mean +/- SD) months after heart transplantation. Transplant patients were assigned to groups with diffusion > 70% (n = 5) or diffusion < 70% of predicted values (n = 5). The control group and both subsets of patients performed 10 min of cycle exercise at 40% and 70% of peak power output. Arterial blood gases were drawn every 30 s during the 1st 5 min and at 6, 8 and 10 min.

RESULTS

Significant improvements in forced vital capacity (17.4%), forced expiratory volume in 1 s (11.7%) and diffusion capacity (6.6%) occurred in the patients; however, posttransplantation vital capacity, forced expiratory volume and diffusion were lower (p < or = 0.05) compared with values in 11 matched control subjects. Changes in blood gases were similar among groups at 40% of peak power output. At 70% of peak power output, arterial blood gases and pH were significantly (p < or = 0.05) lower in transplant patients with low diffusion (arterial oxygen pressure 15 to 38 mm Hg below baseline) than in patients with normal diffusion and control subjects. Cardiac index did not differ (p > or = 0.05) between transplant patients with normal and low diffusion at rest or during exercise. Posttransplantation mean pulmonary artery pressure was significantly related to exercise-induced hypoxemia (r = 0.71; p = 0.03).

CONCLUSIONS

Abnormal pulmonary diffusion observed in patients before heart transplantation persists after transplantation with or without restrictive or obstructive ventilatory defects. Heart transplant recipients experience exercise-induced hypoxemia when diffusion at rest is < 70% of predicted. Our data also suggest that abnormal pulmonary gas exchange possibly contributes to diminished peak oxygen consumption in some heart transplant recipients; however, direct testing of this hypothesis was beyond the scope of the present study. This possibility needs to be investigated further.

Endothelial dysfunction early after heart transplantation. Assessment with intravascular ultrasound and Doppler

BACKGROUND

Allograft vasculopathy after heart transplantation is thought to represent a response to endothelial injury in the graft vessels. To assess endothelial function before the onset of anatomic disease, coronary vasomotor responses to adenosine, acetylcholine, and nitroglycerin were evaluated in transplant recipients by intravascular ultrasound imaging and Doppler flow studies.

METHODS AND RESULTS

Nine patients were studied 1 year after heart transplantation. Acetylcholine provoked significant vasoconstriction to 82% of maximal coronary diameter but was associated with an increase in mean coronary blood flow from 63.1 to 204 ml/min. Coronary blood flow increased fivefold in response to adenosine, a normal response.

CONCLUSIONS

The vasomotor response to acetylcholine at 1 year after heart transplantation is consistent with endothelial dysfunction in the epicardial conduit vessels. Microvascular function as judged by coronary flow reserve appears to be normal.

Management of the patient awaiting cardiac transplantation

The spectacular clinical success of heart transplantation (HTTX) in the cyclosporine era has engendered challenging new clinical problems that include long-term management of patients with severely compromised systolic function, preparation of potential HTTX recipients for major surgery followed by immunosuppression, and ethical and rational distribution of limited numbers of donated organs. The magnitude of these challenges may seem overwhelming. Fortunately, clinicians have the luxury of dealing with the issues involved one patient, and one step, at a time. The continued efforts of clinical investigators have clarified important management principles. There is a growing appreciation of the pivotal importance of mitral valve function in determining the response to medical therapy and long-term prognosis in this patient population. Enthusiasm for pharmacologic control of asymptomatic ventricular ectopy has waned; instead, the restoration and maintenance of normal atrial function has clearly taken precedence. In preparation for surgery, new endoscopic techniques offer great advantages. The use of high-technology support devices as "bridges to transplantation" has been re-examined in view of the relatively poorer short- and long-term prognosis of patients managed with these devices. Increasingly, the optimal scenario for HTTX entails transplantation of a severely compromised but medically stable patient. As specific therapy, HTTX today has relatively limited application to the vast majority of patients with heart failure (HF). Seventeen hundred heart transplants will do little to directly affect the 400,000 patients in the United States who each year develop symptomatic HF.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative analysis of nitroglycerin-induced coronary artery vasodilation in transplanted hearts

Quantitative serial coronary angiograms performed annually over a 3-year period after transplantation in 26 orthotopic heart transplant recipients showed persistently normal nitroglycerin-induced vasodilation. The vasodilator response to nitroglycerin did not predict development of graft arteriopathy; the presence of graft arteriopathy did not prevent a substantial vasodilator response to nitroglycerin.

Serial quantitative coronary angiography in the assessment of coronary disease in the transplanted heart

Quantitative angiographic studies with use of cine-videodensitometry after maximal coronary vasodilation with nitroglycerin in 18 "angiographically normal" heart transplant recipients demonstrated significant loss of lumen diameter between years 1 and 3. When sensitive angiographic techniques are used, graft arteriopathy appears to be ubiquitous in heart transplant recipients.