The role of angiotensin receptor blockers in the management of chronic heart failure.

Clinical and basic science research has repeatedly confirmed the importance of the renin-angiotensin-aldosterone system in the pathophysiology of chronic heart failure. Accordingly, blockade of this system by angiotensin-converting enzyme (ACE) inhibitors has assumed a central role in the treatment of heart failure. Recently, angiotensin II receptor blockers (ARBs) have gained prominence as a possible substitute for ACE inhibitors in therapy for heart failure. However, clinical data compiled on this use of ARBs have shown them to be useful only as alternative therapy in ACE inhibitor-intolerant patients. Continuing large-scale clinical investigations may lead to an expansion of their role in therapy for various cardiovascular diseases.

Prospective study of the circadian pattern of blood pressure after heart transplantation.

BACKGROUND: Previous reports indicate that heart transplant recipients lack a normal nocturnal decline in blood pressure. This prospective study was designed to determine the evolution of circadian blood pressure patterns after heart transplantation. METHODS: Twenty-four-hour ambulatory blood pressure and heart rate was measured in eight heart transplant recipients early (47 +/- 35 days) and late (740 +/- 10 days) after transplantation. RESULTS: Early transplant recordings and the normal control group recordings showed similar daytime systolic blood pressure but had different nighttime systolic blood pressure (138 +/- 15 mm Hg versus 112 +/- 9 mm Hg, p = 0.0002). The percent nocturnal change in systolic blood pressure showed a nocturnal increase in blood pressure in the early recordings versus a decrease in the healthy subjects (+4 +/- 2.7 versus -13 +/- 5.4, p < 0.0001). The late recordings showed a significant decrease in the nighttime systolic blood pressure (138 +/- 15 mm Hg versus 119 +/- 7 mm Hg, p = 0.011). The percent nocturnal change in systolic blood pressure was also significantly different between the early and late recordings (+4 +/- 2.7 versus -9 +/- 9, p = 0.0082) indicating a return of a nocturnal decline in systolic blood pressure. Similar patterns in diastolic blood pressure were observed. No significant change in the percent nocturnal change in heart rate occurred (-10 +/- 4.1 versus -7 +/- 5.5). CONCLUSIONS: Prospective follow-up of this heart transplant population showed that diurnal blood pressure variation is restored in some patients; diurnal variation is not related to corticosteroids, cyclosporine, or heart rate.

Role of spectral measures of heart rate variability as markers of disease progression in patients with chronic congestive heart failure not treated with angiotensin-converting enzyme inhibitors.

Measures of heart rate variability in the frequency domain quantify autonomic activity. However, the relation of these measures to the severity of ventricular dysfunction in patients with congestive heart failure remains uncertain. We applied spectral analysis of heart rate variability to 24-hour Holter monitor recordings obtained from 20 patients with congestive heart failure who were not treated with angiotensin-converting enzyme inhibitors to determine whether significant changes in parameters of heart rate variability reflect the progression of symptoms in patients with ventricular failure. Both total and low-frequency heart rate spectral power were seen to decrease with worsening New Heart Associate (NYHA) functional class. A significant (p = 0.04) higher total power was noted in NYHA class II than in class III patients (3.0 x 10(-3) +/- 3.6 10(-4) and 2.5 x 10(-3) +/- 5.9 x 19(-4) [beats/min]2, respectively). Similarly, low-frequency heart rate spectral power was significantly (p = 0.008) higher in class II than in class III patients (1.7 x 10(-3) +/- 4.6 x 10(-4) and 1.1 x 10(-3) +/- 3.5 x 10(-4) [beats/min]2, respectively). Only the low-frequency component of the spectrum was directly correlated with left ventricular ejection fraction (LVEF) (r = 0.40) with a trend toward statistical significance (p = 0.07). Measures of heart rate variability and the changes in autonomic tone that they reflect may therefore serve as markers of the extent of disease progression in patients with congestive heart failure.

Differing autonomic response to dobutamine in the presence and absence of ischemia: implications for the autonomic contribution to positive inotropic intervention.

Although it is well recognized that dobutamine is a powerful positive inotropic agent mediating increased myocardial contractility through direct beta-adrenergic stimulation, the mechanism of its overall circulatory effects appears more complex than that which may be ascribed solely to this direct action on the myocardium. Previous investigations have implied that reflex alterations in autonomic balance may contribute significantly to the response to this agent, but direct evidence describing such a response has not been reported. The objective of this investigation was to assess changes in autonomic tone induced by dobutamine in the presence and absence of ischemia through the measurement of heart rate variability in patients undergoing dobutamine stress echocardiography. Of 25 consecutive patients undergoing dobutamine stress echocardiography, 16 were found to have unequivocal evidence for or against the presence of ischemia during dobutamine infusion. Heart rate data from these 16 patients were submitted for spectral analysis of heart rate variability and quantification of parasympathetically governed high-frequency heart rate variability and sympathetically influenced low-frequency heart rate variability. Of the 16 patients nine were not found to have evidence for ischemia (group 1), and seven were found to have echocardiographic findings consistent with dobutamine-induced ischemia (group 2). The two groups significantly differed (p = 0.04) in the change in parasympathetic tone associated with dobutamine with a significant (p = 0.04) increase in parasympathetic tone in group 1 and a numeric decrease in group 2. A significant (p = 0.04) decrease in sympathetic tone was noted in group 1 as reflected by low-frequency heart rate variability with a numeric increase in this measure in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of autonomic tone over a 24-hour period in patients with congestive heart failure: relation between mean heart rate and measures of heart rate variability.

Patients with congestive heart failure (CHF) are characterized by an imbalance of the autonomic nervous system, which may contribute to the progression of circulatory failure and influence survival. However, it is still unclear whether CHF is characterized by a suppression of the diurnal variation in autonomic tone that is observed in normal subjects. To characterize the circadian variation in autonomic tone in patients with ventricular failure, ambulatory 24-hour Holter monitor recordings were obtained in 20 patients with CHF; 4-minute epochs of data from every hour of each 24-hour recording were selected. For each epoch we calculated the mean heart rate (HR) and, by applying spectral analysis of heart rate variability (HRV), we quantified the magnitude of the total (0.02 to 0.9 Hz), sympathetically governed low frequency variability (0.02 to 0.1 Hz), and parasympathetically mediated high-frequency variability (0.1 to 0.9 Hz). These areas were also expressed as a ratio to total variability and a ratio of high to low variability. A highly significant change in the mean HR over 24 hours was observed (p = 0.0001); no changes in the measures of HRV were obtained (p < 0.3). No significant correlation was found between mean HR and any frequency domain measures. We conclude that the sustained imbalance of autonomic tone over a 24-hour period, as shown by the spectral analysis of HRV, may promote the progression of circulatory failure and predispose patients with CHF to malignant ventricular arrhythmias and sudden cardiac death.(ABSTRACT TRUNCATED AT 250 WORDS)