Predicting death from progressive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

Prediction of cardiac death in patients with a very low ejection fraction after myocardial infarction: a Cardiac Arrhythmia Suppression Trial (CAST) study

The Cardiac Arrhythmia Suppression Trial (CAST) database was analyzed with a Cox proportional hazards regression model to predict the mortality of patients with very poor left ventricular systolic function (ejection fraction < or = .20). Predictors of total death or cardiac arrest were (relative risk), QRS duration (1.10/10 msec increase), coronary artery bypass grafting (0.38), basal heart rate (1.26/10 min-1 increase), diastolic blood pressure (0.79/10 mm Hg increase), diabetes mellitus (1.59), EF (0.94/1 U increase), and ease of suppression (the ability to suppress ambient ventricular ectopy on the lowest dose of the first randomly chosen CAST drug) (0.64). Predictors of arrhythmic death or arrhythmic cardiac arrest included thrombolysis (0.44), coronary artery bypass grafting (0.38), diuretic use (1.71), heart rate (1.21/10 min-1 increase), calcium channel blocker use (1.69), and QRS duration (1.10/10 msec increase). Thus easily measurable clinical and laboratory variables help predict prognosis in this clinically important subgroup. The pathophysiologic basis for and the clinical implications of the ease of ventricular arrhythmia suppression correlating with prognosis requires further study.

Implantable defibrillators for high-risk patients with heart failure who are awaiting cardiac transplantation

The objective of this study was to assess the operative risk and efficacy of implantable defibrillators for preventing sudden death in patients with heart failure awaiting transplantation. The average waiting time for elective cardiac transplantation is 6 months to 1 year. Sudden cardiac death is the major source of mortality in outpatients in stable condition awaiting cardiac transplantation. The efficacy of implantable defibrillator therapy in this population is not established. We analyzed the operative risk, time to appropriate shock, and sudden death in 15 patients determined to be at high risk of sudden death who were accepted onto the outpatient cardiac transplant waiting list. Nonfatal postoperative complications occurred in two (13%) subjects with epicardial defibrillating lead systems and in none with transvenous lead systems. Defibrillation energies were 16 +/- 2 J versus 24 +/- 2 J with epicardial and transvenous lead systems, respectively. Sudden death free survival until transplantation was 93%. Most of the patients (60%) had an appropriate shock during a mean follow-up of 11 +/- 12 months. The mean time to an appropriate shock was 3 +/- 3 months. Hospital readmission was required in three (20%) subjects to await transplantation on an urgent basis. However, two of these subjects had received appropriate shocks before readmission. In selected patients at high risk for sudden death while on the outpatient cardiac transplant waiting list, the operative risk is low and adequate defibrillation energies can be obtained to allow implantable defibrillator placement. Most subjects will have an appropriate shock as outpatients before transplantation, and sudden death free survival is excellent.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation between peak exercise oxygen consumption and hemodynamic dysfunction in potential heart transplant candidates

OBJECTIVES

The purpose of this study was to determine how often peak exercise oxygen consumption (VO2) misclassifies the severity of cardiac dysfunction in potential heart transplant candidates.

BACKGROUND

Cardiopulmonary exercise testing is being used to help select heart transplant candidates on the basis of the assumption that a low peak exercise VO2 indicates severe hemodynamic dysfunction and a poor prognosis. However, noncardiac factors, such as muscle deconditioning, can also influence exercise capacity. Therefore, peak exercise VO2 may overestimate the severity of cardiac dysfunction in some patients.

METHODS

Hemodynamic and respiratory responses to maximal treadmill exercise were measured in 64 sequential patients undergoing evaluation for heart transplantation, all of whom had an ejection fraction < 35% and reduced peak exercise VO2 levels (mean [+/- SD] 13.3 +/- 2.7 ml/min per kg).

RESULTS

Twenty-eight (44%) of 64 patients exhibited a reduced cardiac output response to exercise and pulmonary wedge pressure > 20 mm Hg at peak exercise, consistent with severe hemodynamic dysfunction. Twenty-three patients (36%) exhibited a normal cardiac output response to exercise but a wedge pressure > 20 mm Hg at peak exercise, suggesting moderate hemodynamic dysfunction. Thirteen patients (20%) exhibited a normal cardiac output and wedge pressure < 20 mm Hg at peak exercise, suggesting mild hemodynamic dysfunction. Despite these markedly different hemodynamic responses, all three groups exhibited similar peak exercise VO2 levels (mild dysfunction 14.2 +/- 3.5 ml/min per kg, moderate dysfunction 13.9 +/- 2.7 ml/min per kg, severe dysfunction 12.4 +/- 2.1 ml/min per kg). A peak exercise VO2 level < 14 ml/min per kg, considered to reflect severe hemodynamic dysfunction, was observed in 18 of the patients with a normal cardiac output response to exercise, whereas 7 patients with severe hemodynamic dysfunction had a peak VO2 level > 14 ml/min per kg.

CONCLUSIONS

More than 50% of potential heart transplant candidates with a reduced peak exercise VO2 level exhibit only mild or moderate hemodynamic dysfunction during exercise. Hemodynamic responses to exercise should be directly measured in potential transplant candidates to confirm severe circulatory dysfunction.

Dissociation between exertional symptoms and circulatory function in patients with heart failure

BACKGROUND

Patients with heart failure frequently report exertional dyspnea and fatigue. These symptoms are usually attributed to circulatory dysfunction and therefore are typically treated with cardiovascular medications. Serial assessment of exertional symptoms has also become the principal method used to assess drug efficacy in heart failure. Nevertheless, the relation between exertional symptoms in heart failure and circulatory dysfunction remains uncertain.

METHODS AND RESULTS

This study was undertaken to investigate the relation between exertional symptoms, ventilatory and skeletal muscle dysfunction, and circulatory function in patients with heart failure. To this end, 52 ambulatory patients with heart failure underwent hemodynamic monitoring during maximal treadmill exercise testing. During exercise, the severity of dyspnea and fatigue was evaluated on a scale of 6 to 20 (Borg scale). The level of perceived exercise intolerance during daily activities was evaluated with the Minnesota Living With Heart Failure Questionnaire and the Yale Dyspnea-Fatigue Index. Maximal treadmill exercise increased the VO2 to 13.4 +/- 2.8 mL.min-1.kg-1, the dyspnea score to 15.7 +/- 2.3, the fatigue score to 14.8 +/- 3.4, the pulmonary wedge pressure to 28 +/- 11 mm Hg, and the pulmonary artery lactate concentration to 34.5 +/- 16.3 mg/dL and decreased the pulmonary artery hemoglobin oxygen saturation to 30 +/- 9%. The level of perceived dyspnea had no relation to the pulmonary wedge pressure and correlated only minimally with the level of excessive ventilation (r = 39). The level of perceived fatigue correlated only weakly with blood lactate concentration (r = .55). Eleven patients (21%) exhibited a normal cardiac output and wedge pressure < 20 mm Hg during exercise, 22 (42%) exhibited a normal cardiac output but wedge pressure > 20 mm Hg during exercise, and 19 (37%) exhibited reduced cardiac output and wedge pressure > 20 mm Hg during exercise. Despite these markedly different hemodynamic responses, all three groups exhibited similar levels of fatigue and dyspnea at comparable workloads and had comparable total scores for the Minnesota Living With Heart Failure Questionnaire and the Yale Dyspnea-Fatigue Index. There was no relation between the Living With Heart Failure Questionnaire and peak exercise VO2 and only a weak correlation between the Dyspnea-Fatigue Index and peak VO2 (r = .48).

CONCLUSIONS

The level of exercise intolerance perceived by patients with heart failure has little or no relation to objective measures of circulatory, ventilatory, or metabolic dysfunction during exercise. In patients who report severe exertional symptoms, it may be desirable to directly measure hemodynamic response to exercise to ensure that these symptoms are due to circulatory dysfunction.

Preserved right ventricular ejection fraction predicts exercise capacity and survival in advanced heart failure

OBJECTIVES

This study was undertaken to determine which exercise and radionuclide ventriculographic variables predict prognosis in advanced heart failure.

BACKGROUND

Although cardiopulmonary exercise testing is frequently used to predict prognosis in patients with advanced heart failure, little is known about the prognostic significance of ventriculographic variables.

METHODS

The results of maximal symptom-limited cardiopulmonary exercise testing and first-pass radionuclide ventriculography in patients with advanced heart failure referred for evaluation for cardiac transplantation were analyzed.

RESULTS

Sixty-seven patients with advanced heart failure (mean [+/- SD]; age 51 +/- 10 years, New York Heart Association functional classes III (58%) and IV (18%); mean left ventricular ejection fraction 0.22 +/- 0.07) underwent simultaneous upright bicycle ergometric cardiopulmonary exercise testing and first-pass rest/exercise radionuclide ventriculography. Mean peak oxygen consumption (VO2) was 11.8 +/- 4.2 ml/kg per min, and mean peak age- and gender-adjusted percent predicted oxygen consumption (%VO2) was 38 +/- 11.9%. Univariate predictors of overall survival included right ventricular ejection fraction > or = 0.35 at rest and > or = 0.35 at exercise and %VO2 > or = 45% (all p < 0.05). In a multivariate proportional hazards survival model, right ventricular ejection fraction > or = 0.35 at exercise (p < 0.01) and %VO2 > or = 45% (p = 0.01) were selected as independent predictors of overall survival. Univariate predictors of event-free survival included right ventricular ejection fraction > or = 0.35 at rest (p = 0.01) and > or = 0.35 at exercise (p < 0.01), functional class II (p < 0.05) and %VO2 > or = 45% (p = 0.05). Right ventricular ejection fraction > or = 0.35 at exercise (p = 0.01) was the only independent predictor of event-free survival in a multivariate proportional hazards model. Cardiac index at rest, VO2, left ventricular ejection fraction at rest, and exercise-related increase or decrease > 0.05 in left or right ventricular ejection fraction were not predictive of overall or event-free survival in any univariate or multivariate analysis.

CONCLUSIONS

1) Right ventricular ejection fraction > or = 0.35 at rest and exercise is a more potent predictor of survival in advanced heart failure than VO2 or %VO2; 2) %VO2 rather than VO2 predicts survival in advanced heart failure; 3) neither %VO2 nor VO2 predicts survival to the combined end point of death or admission for inotropic or mechanical support in patients with advanced heart failure.

Innovations in pulse generators and lead systems: balancing complexity with clinical benefit and long-term results

Technologic development of implantable cardioverter defibrillators (ICDs) is now in an exponential growth phase, and many new concepts are being examined. Major innovations have occurred in pulse generators and in lead systems. This may increase ICD use for primary and secondary prevention of sudden cardiac death. Pulse generators now include hybrid pacemaker-defibrillators. Clinical data suggest a need for demand pacing in primary and secondary prevention applications, with antitachycardia pacing being most valuable in the latter group. Atrial leads will allow dual chamber sensing, pacing, and defibrillation. Low energy cardioversion with biphasic shocks can enhance shock efficacy in rapid monomorphic ventricular tachycardia and flutter. Modifications of lead design, biphasic shock waveforms, and optimal thoracic electrode location in axillary or pectoral regions will permit lower energy defibrillation and smaller pulse generators with lower maximum energy outputs of < or = 25 joules. Dual chamber sensing will improve detection of atrial flutter or fibrillation. Minimum data storage requirements for tachycardia events in ICDs still need to be defined. Intracardiac electrogram analysis is still in evolution, and better analytic methods are awaited. Lead system development is likely to support generic pacing and defibrillation catheter electrodes for atrial and ventricular application. Advances in thoracic electrode design are in progress, and a variety of intercostal electrodes are being tested. Improvements in lead design with further impact on defibrillation energy requirements have the potential to permit generator miniaturization. Significant technologic improvements in ICD devices are imminent and should improve clinical results, patient safety, and quality of life.