Last Updated: 2008-01-02 15:16:33 -0400 (Reuters Health)
NEW YORK (Reuters Health) – Findings published in the December issue of Neurology suggest that post-acute stroke patients exhibit a parasympathetic cardiac deficit that may put them at risk of cardiac arrhythmia because of unopposed sympathetic stimulation.
"Autonomic dysregulation is frequent in acute ischemic stroke," write Dr. Max J. Hilz and colleagues from the University of Erlangen-Nuremberg, Germany. "Several studies concluded that imbalance between sympathetic and parasympathetic cardiovascular function predisposes to malignant cardiac arrhythmia," they note. "However, there are few data on cardiovascular autonomic function in post-acute stroke patients."
In the current study, the researchers examined cardiovascular autonomic function 18 to 43 months (median 31 months) after lacunar stroke. They also assessed the influence of the side of the ischemia on cardiovascular autonomic function by including 15 patients (median age 63 years) with right-sided lacunar stroke, 13 patients (median age 68 years) with left-sided lacunar stroke, and 21 age- and sex-matched controls.
The investigators monitored heart rate recorded as R-R intervals (RRint), mean blood pressure (BPmean), and respiration. Autoregressive spectral analysis was used to evaluate sympathetic and parasympathetic modulation as powers of RRint and BPmean oscillations in the low-frequency (LF: 0.04 to 0.15 Hz) and high-frequency bands (HF: 0.15 to 0.5 Hz).
There were no differences between patients with right- or left-sided strokes and controls in mean values of RRint, BPmean, and respiration rates.
However, a trend toward elevated LF power of RRint was observed in patients with right-sided stroke as compared to those with left-sided stroke and controls. HF powers of RRint were reduced in patients with right- and left-sided stroke as compared with controls, but there was no differences between patients with right- or left-sided stroke.
"LF/HF ratio of RRint was elevated in patients with right-sided infarction as compared with controls (p = 0.001)," Dr. Hilz and colleagues report. "In contrast, there was no difference between the LF/HF ratio of patients with right- or left-sided infarction or between the LF/HF ratio of patients with left-sided infarction and controls."
The investigators conclude that the study demonstrates two major findings in post-acute stroke patients: lower parasympathetic tone, and a tendency toward increased sympathetic cardiac modulation in patients with right-sided strokes.
"Larger, prospective studies are needed," they conclude, "to assess the association between decreased cardiovascular autonomic function and cardiac mortality risk in patients with lacunar strokes in more detail."