Beta-adrenergic blockers as cardioprotective agents

Spinal cord injury alters cardiac electrophysiology and increases the susceptibility to ventricular arrhythmias

The autonomic nervous system modulates cardiac electrophysiology and abnormalities of autonomic function are known to increase the risk of ventricular arrhythmias. The abnormal and unstable autonomic control of the cardiovascular system following spinal cord injury also is well known. For example, individuals with mid-thoracic spinal cord injury have elevated resting heart rates, increased blood pressure variability, episodic bouts of life-threatening hypertension as part of a condition termed autonomic dysreflexia, and elevated sympathetic activity above the level of the lesion. Furthermore, cardiovascular morbidity and mortality are high in individuals with spinal cord injuries due to a relatively sedentary lifestyle and higher prevalence of other cardiovascular risk factors, including obesity and diabetes. Therefore, spinal cord injury may alter cardiac electrophysiology and increase the risk for ventricular arrhythmias. In this chapter, we discuss how the autonomic changes associated with cord injury can influence cardiac electrophysiology and the susceptibility to ventricular arrhythmias.

Health outcomes associated with beta-blocker and diltiazem treatment of unstable angina

OBJECTIVE

We compared long-term health outcomes associated with beta-adrenergic blocking agents and diltiazem treatment for unstable angina.

BACKGROUND

No long-term data have been published comparing these two antianginal treatments in this setting.

METHODS

Eligible veterans were discharged from the Veterans Affairs Puget Sound Health Care System (VAPSHCS), Seattle Division, between October 1989 and September 1995 with an unstable angina diagnosis and were prescribed monotherapy beta-blocker or diltiazem treatment at discharge. Medication data were collected from medical records and computerized VAPSHCS outpatient pharmacy files. Follow-up death and coronary artery disease rehospitalization data were collected through 1996. Proportional hazards regression compared survival among diltiazem and beta-blocker users, controlling for patient characteristics with propensity scores.

RESULTS

Two hundred forty-seven veterans (24% on beta-blockers, 76% on diltiazem) were included in this study. There were 54 (22%) deaths during an average follow-up of 51 months. After propensity score adjustment, there was no difference in risk of death comparing diltiazem to beta-blocker treatment (hazards ratios [HR] 1.1; 95% confidence interval [CI] 0.49 to 2.4). Among Washington residents (n=207), there were 146 (71%) coronary artery disease rehospitalizations or deaths during follow-up. After adjustment, there was a nonsignificant increase in risk of rehospitalization or death associated with diltiazem use (HR 1.4; 95% CI 0.80 to 2.4). For both analyses, similar risks were found among veterans without relative contraindications to beta-blockers.

CONCLUSIONS

We found no survival benefit of diltiazem over beta-blocker treatment for unstable angina in this cohort of veterans.

Sotalol for ventricular tachyarrhythmias: beta-blocking and class III contributions, and relative efficacy versus class I drugs after prior drug failure. ESVEM Investigators. Electrophysiologic Study Versus Electrocardiographic Monitoring

In the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial, d,l-sotalol was associated with a lower arrhythmia recurrence and mortality than class I antiarrhythmic drugs. To further evaluate the relative efficacy of d,I-sotalol compared with class I drugs, and to assess the relative importance of its class II (beta-blocking) and class III effects, 6-year arrhythmia recurrence and mortality in patients receiving sotalol were compared with those in patients receiving class I drugs, subdivided according to whether they also received coadministered beta blockers. Relative efficacy was also determined for sotalol and for class I drugs as stratified by the presence/absence of prior drug failure. Arrhythmia recurrence was lower for the 84 patients receiving sotalol than for patients given class I agents with (n = 28) (p = 0.008) or without (n = 184) (p = 0.001) alpha beta blocker. Mortality was lower for patients taking sotalol than for those given a class I drug without alpha beta blocker (p = 0.034), but similar (p = 0.835) if alpha beta blocker was also administered. In contrast to class I drugs, which had lower efficacy rates when prior drug trials had failed, sotalol maintained its efficacy despite prior drug failures preceding or during the ESVEM trial. Both class II and III actions in the ESVEM trial were important to the clinical superiority of sotalol in the treatment of ventricular tachyarrhythmias.