High NIHSS scores after stroke onset suggest increased risk of sympathetic cardiac complications

Background: After acute stroke, cardiac complications might frequently result from dysfunction of the central autonomic network (CAN) (1). Cardiac risk may account for poor outcome but is often not readily diagnosed. We assume that CAD severity correlates with severity of acute stroke.

Objective: To evaluate whether clinical severity after stroke onset as determined by the NIHSS correlates with CAD severity.

Patients and Methods: In 15 patients (5 women, mean age 74.4±9.9 years) with acute middle cerebral artery ischemic stroke (8 left-, 7 right-hemispheric), we assessed NIHSS within the first 50–540 minutes (mean 238±174min) after stroke onset, and continuously monitored heart rate as RR-intervals (RRI). From 90-second-segments, we determined spectral powers of underlying RRI oscillations in the parasympathetically mediated high- (RRI-HF: 0.04–0.15Hz) and mainly sympathetically mediated low- (RRI-LF: 0.15–0.5Hz) frequency bands using trigonometric regressive spectral analysis. We calculated the LF/HF-ratio as index of sympathovagal balance, and the sum of LF- and HF-powers as approximation of total power of autonomic RRI modulation. We correlated LF-, HF-, total powers and LF/HF-ratios with NIHSS scores (Pearson R; Significance: p<0.05).

Results: Patients had NIHSS scores of 0–21 (median: 6; lower quartile: 3; upper quartile: 13), powers of RRI-LF at 149.6±146.5ms² and RRI-HF at 70.9±62.9ms²; RRI-total powers were 199.9±178.2ms², LF/HF- ratios were 3.9±4.9. Correlation between NIHSS scores and RRI-LF-powers was not significant. Correlations were highly significant between NIHSS scores and RRI-HF powers (R=-0.638; p=0.01), LF/HF-ratios (R=0.729, p=0.002), and total powers (R=-0.547, p=0.03).

Conclusion: Shortly after stroke onset, higher NIHSS correlated with more prominent increases in sympathetic cardiac modulation and more prominent decreases in parasympathetic as well as total autonomic modulation of heart rate. The higher sympathetic tone with less parasympathetic buffering capacity and decreased overall ability to adjust heart rate poses an increased risk of cardiac complications. Our preliminary data suggest that high NIHSS scores at admission indicate a high risk of sympathetically mediated cardiac complications and require special attention towards such events.

Reference: (1) Hilz MJ, Schwab S. Stroke 2008;39:2421–2.

Acknowledgement: The study was partially supported by the International Brain Research Foundation, IBRF, Inc., Edison, NJ, USA.