Publications by Year: 2011

BACKGROUND: Chronic hemodialysis (HD) patients have an elevated risk of sudden cardiac death (SCD), particularly in the 24 hours before the first HD of the week. Temporal changes in cardiac autonomic dysfunction, as characterized by abnormalities in heart rate variability (HRV) and heart rate turbulence (HRT), along with T-wave alternans (TWA), may contribute to this dispersion of risk.

OBJECTIVE: This study sought to determine the prevalence of abnormal HRV, HRT, and TWA in HD patients and to compare their temporal distribution among periods of variable SCD risk.

METHODS: HRV, HRT, and TWA were analyzed from 72-hour Holter monitors in HD patients, and results were compared among the 24-hour high-risk period before the first dialysis session of the week, the 24-hour intermediate-risk period beginning with the weeks' first dialysis, and the low-risk period the day after the first dialysis. Positive cut points were standard deviation of all normal R-R intervals ≤70 ms for HRV, onset ≥0% and/or slope ≤2.5 ms/R-R for HRT, and ≥53 μV for TWA.

RESULTS: Of 41 enrollees, 28 (46% male, age 55 ± 12, ejection fraction 57% ± 11%) had sufficient data for analysis. Abnormalities were prevalent with 82%, 75%, and 96% of patients reaching threshold for HRV, HRT, and TWA in at least one 24-hour period, respectively. There was no significant difference in the prevalence of abnormal measures among dialytic intervals nor in the intraindividual distribution of abnormal measures (P >.05 for all).

CONCLUSION: Abnormal HRV, HRT, and TWA are prevalent in HD patients and may indicate heightened SCD risk. No significant correlation was observed among these measures and recognized periods of variable risk.

Despite the increased risk of myocardial infarction, aortic dissection, and arrhythmias in patients with hypertension who use cocaine, the hemodynamic and arrhythmogenic effects of cocaine use have not been well characterized in this population. The authors hypothesized that patients with hypertension demonstrate extreme, transient changes in arterial pressures as well as new arrhythmic activity during cocaine use. Ambulatory blood pressures, heart rates, and electrocardiograms (AECGs) were recorded for 48 hours in 10 patients with a history of hypertension who smoke cocaine. Active cocaine use was identified through patient diaries and manual activation of the blood pressure cuff. Of the 10 patients studied (6 men, 7 African Americans, age 49±8 years), 8 were taking antihypertensive medications. The mean blood pressure prior to cocaine use was 126/77 mm Hg and average increase in systolic, diastolic, and mean arterial pressure after use was 74 mm Hg, 30 mm Hg, and 45 mm Hg, respectively (P<.0001 for all). There was no significant change in heart rate. AECGs demonstrated arrhythmic activity during cocaine use, including 6 patients with increased atrial and ventricular ectopy, 2 patients with episodes of nonsustained atrial tachycardia, and 1 patient with 3 episodes of nonsustained monomorphic ventricular tachycardia. Cocaine use resulted in extreme elevations in arterial pressures in patients with hypertension taking medication. Cocaine use was also associated with an increase in arrhythmic activity. These findings may underlie the heightened risk of myocardial infarction, aortic dissection, and potentially lethal arrhythmias in patients with hypertension who use cocaine.