Chronotropic incompetence: when should a pacemaker be considered? Which pacing system and which settings?

Chronotropic incompetence is defined as the inability to increase and maintain heart rate appropriately during exercise. Intolerance to exertion is manifested by a number of clinical symptoms, and is almost obligatory if heart rate cannot be increased. Several rate-modulating pacing systems have been developed. The most obvious and reliable way to increase heart rate during exercise is to detect the sinus node. Adding an atrial lead in a patient in complete AV block and VVI pacing is the most satisfactory way to correct chronotropic incompetence in some patients. Rate-adaptive sensors include motion sensors, respiration sensors, QT interval, and right ventricular contractility. Indications for rate-adaptive pacing should be based on clinical symptoms, demonstration of a lack of cardiac acceleration during exercise, and the presence of another indication for pacing.     

Thromboembolism in heart failure: who should be treated?

The risk of thromboembolic complications in patients with heart failure and/or chronic left-ventricular systolic dysfunction is increased. Nevertheless, anticoagulant therapy in these patients is still a subject of debate. Atrial fibrillation is the only prospectively evaluated, proven thromboembolic risk factor and patients with atrial fibrillation benefit from long term anticoagulant therapy. The significance of other proposed thromboembolic risk factors in heart failure and/or chronic left-ventricular dysfunction such as gender, cause of myocardial disease, severity of heart failure, left-ventricular ejection fraction, left-ventricular thrombus, left ventricular aneurysm and history of previous thromboembolic event is less clear. This article summarizes key studies, assesses the incidence of thromboembolism, evaluates risk factors and proposes guidelines for anticoagulation of patients with heart failure and/or left ventricular systolic dysfunction.     

Serial echocardiographic assessment of left ventricular mass: how blinded should readers be?

OBJECTIVES: In addition to the interest of mixing the sequence of echo-exam in a central blinded review, we studied the effect that might result from group-analysis of all echocardiograms simultaneously for each patient, with their sequence kept blind. A priori, this method of reading has the potential of decreasing measurement variability. METHODS: We included 630 echocardiograms from 210 hypertensive patients participating in a randomized clinical trial comparing two antihypertensive agents for regression of left ventricular (LV) hypertrophy. Three echocardiograms per patient [selection (4 weeks before; W-4), at inclusion (week 0; W0), and the end of treatment (week 52; W52)], were read twice, according to two methods, blind to centre, patient numbers and sequence of visits: (1) examination of individual serial echocardiograms, (2) examination of all-patient mixed echocardiograms. The first method was expected to increase the power of treatment comparison by reducing variability of measurements of left ventricular mass (LVM). RESULTS: Pooling echocardiograms of all patients reduces variability of LVM change under treatment: absolute LVM (W52 - W0) standard deviation was reduced by 22%. Nevertheless, despite a good between-methods agreement for LVM values at each visit (intra-class coefficient of correlation from 0.88 to 0.92), LVM change under treatment was reduced even more, by 41%. Thus, the slight decrease of variability induced by gathering the echocardiograms is associated with an even greater reduction of LVM change. CONCLUSIONS: According to these findings, the 'full-blind' methodology for a central blinded review in clinical trials appears to produce the maximum power of the study with the lowest sample size.     

Does left ventricular shape influence clinical outcome in heart failure?

BACKGROUND: Left ventricular (LV) shape tends to become spherical in patients with dilated cardiomyopathy of diverse etiology. Clinical and echocardiographic factors which affect the degree of LV spherical distortion and the impact of altered LV shape on prognosis have not been studied adequately. HYPOTHESIS: This study was undertaken to investigate the prognostic implications of altered LV shape on clinical outcome in dilated cardiomyopathy. METHODS: In 112 patients with depressed LV ejection fraction (19 +/- 9%) and symptomatic heart failure, and in 10 age- and gender-matched normal controls, we performed 2-dimensional echocardiography to assess LV shape using the eccentricity index. Eccentricity index was defined as the ratio of the LV long axis to the LV transverse diameter, measured at end systole and end diastole in the apical four-chamber view. We sought univariate and multivariate clinical and echocardiographic correlates of LV shape. Further, we sought correlations between eccentricity index and clinical outcomes (death and composite outcome of death or emergent heart transplant). RESULTS: Compared with controls, patients with cardiomyopathy had significantly lower systolic (2.04 vs. 1.56; p = 0.001) and diastolic (1.75 vs. 1.53; p = 0.003) eccentricity index, implying a more spherical LV shape. Of all clinical and echocardiographic variables tested, mitral regurgitation, right ventricular dysfunction, and increased LV mass were independently associated with spherical LV shape. At a follow-up period of 17 +/- 12 months, no correlation was found between eccentricity index and the occurrence of death or the combined endpoint of death or emergent heart transplant, in univariate or multivariate analysis. CONCLUSIONS: In patients with dilated cardiomyopathy, the degree of spherical distortion of the LV does not correlate with prognosis.     

Ischemic versus non-ischemic heart failure: should the etiology be determined?

In epidemiological surveys and in large-scale therapeutic trials, the prognosis of patients with ischemic heart failure is worse than in patients with a non-ischemic etiology. Even heart transplant candidates may respond better to intensified therapy if they have non-ischemic heart failure. The term 'non-ischemic heart failure' includes various subgroups such as hypertensive heart disease, myocarditis, alcoholic cardiomyopathy and cardiac dysfunction due to rapid atrial fibrillation. Some of these causes are reversible. The therapeutic effect of essential drugs such as angiotensin-converting enzyme inhibitors, beta-blockers and diuretics does not, in general, significantly differ between ischemic and non-ischemic heart failure. However, in some trials, response to certain drugs (digoxin, tumor necrosis factor-alpha, inhibition with pentoxifylline, growth hormone and amiodarone) was found to be better in non-ischemic patients. Patients with ischemic heart failure and non-contracting ischemic viable myocardium may, on the other hand, considerably improve following revascularization. In view of prognostic and possible therapeutic differences, the etiology of heart failure should be determined routinely in all patients.     

Increased prevalence of concentric left ventricular hypertrophy in African-Americans: Will an epidemic of heart failure follow?

Left ventricular hypertrophy (LVH), used in this review to denote abnormally increased left ventricular (LV) mass, is an important cardiac trait because of its association with numerous adverse cardiovascular outcomes including myocardial infarction and heart failure. LV mass is typically assessed by noninvasive cardiac imaging (echocardiography or MRI); electrocardiography is an insensitive measure. There are two predominant types of hypertrophy: concentric, where LV wall thickness is increased relative to cavity dimensions, and eccentric, where LV wall thickness is not increased relative to cavity dimensions. Several large studies indicate that the prevalence of concentric LVH is higher in African-Americans versus whites. Although there are data to suggest that concentric LVH results in systolic heart failure in animal models, such data are lacking in humans. How concentric LVH affects the prevalence of systolic and diastolic heart failure in African-Americans needs further study. Given the large burden of LVH among African-Americans, such data are needed to estimate the expected burden and type of heart failure which will occur in the future in this population.