The objective of this study was to evaluate whether heart rate variability (HRV) can be used as an index of parasympathetic reactivation after exercise. Heart rate recovery after exercise has recently been shown to have prognostic significance and has been postulated to be related to abnormal recovery of parasympathetic tone. Ten normal subjects [5 men and 5 women; age 33 ± 5 yr (mean ± SE)] exercised to their maximum capacity, and 12 subjects (10 men and 2 women; age 61 ± 10 yr) with coronary artery disease exercised for 16 min on two separate occasions, once in the absence of atropine and once with atropine (0.04 mg/kg) administered during exercise. The root mean square residual (RMS), which measures the deviation of the R-R intervals from a straight line, as well as the standard deviation (SD) and the root mean square successive difference of the R-R intervals (MSSD), were measured on successive 15-, 30-, and 60-s segments of a 5-min ECG obtained immediately after exercise. In recovery, the R-R interval was shorter with atropine ( P < 0.0001). Without atropine, HRV, as measured by the MSSD and RMS, increased early in recovery from 4.1 ± 0.4 and 3.7 ± 0.4 ms in the first 15 s to 7.2 ± 1.0 and 7.4 ± 0.9 ms after 1 min, respectively ( P < 0.0001). RMS (range 1.7–2.1 ms) and MSSD were less with atropine ( P < 0.0001). RMS remained flat throughout recovery, whereas MSSD showed some decline over time from 3.0 to 2.2 ms ( P < 0.002). RMS and MSSD were both directly related ( r2 = 0.47 and 0.56, respectively; P < 0.0001) to parasympathetic effect, defined as the difference in R-R interval without and with atropine. In conclusion, RMS and MSSD are parameters of HRV that can be used in the postexercise recovery period as indexes of parasympathetic reactivation after exercise. These tools may improve our understanding of parasympathetic reactivation after exercise and the prognostic significance of heart rate recovery.

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These data indicate that in normal subjects, parasympathetic effects persist during high-intensity exercise and are prominent in the early phases of recovery. These parasympathetic effects may play an important role in prevention of sudden cardiac death during these periods of increased risk.

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Background Whether percutaneous coronary intervention (PCI) improves clinical outcomes in patients with chronic angina and stable coronary artery disease (CAD) has been a continuing area of investigation for more than two decades. The recently reported results of the International Study of Comparative Health Effectiveness with Medical and Invasive Approaches, the largest prospective trial of optimal medical therapy (OMT) with or without myocardial revascularization, provides a unique opportunity to determine whether there is an incremental benefit of revascularization in stable CAD patients.Methods Scientific databases and websites were searched to find randomized clinical trials (RCTs). Pooled risk ratios were calculated using the random-effects model. ResultsData from 10 RCTs comprising 12 125 patients showed that PCI, when added to OMT, were not associated with lower all-cause mortality (risk ratios, 0.96; 95% CI, 0.87-1.08), cardiovascular mortality (risk ratios, 0.91; 95% CI, 0.79-1.05) or myocardial infarction (MI) (risk ratios, 0.90; 95% CI, 0.78-1.04) as compared with OMT alone. However, OMT+PCI was associated with improved anginal symptoms and a lower risk for revascularization (risk ratios, 0.52; 95% CI, 0.37-0.75). ConclusionsIn patient with chronic stable CAD (without left main disease or reduced ejection fraction), PCI in addition to OMT did not improve mortality or MI compared to OMT alone. However, this strategy is associated with a lower rate of revascularization and improved anginal symptoms.