To the Editor: Dr Young and colleagues1 reported the lack of utility of MPI for predicting myocardial events in the DIAD study. However, the article contained information that suggests a simpler and possibly more effective means of predicting cardiovascular events.
In Table 5, the age- and sex-adjusted hazard ratio for the lowest quartile of cardiac autonomic dysfunction was 4.33 (95% confidence interval, 2.14-8.75; P < .001). A previous article from this group2 reported that an autonomic function test that measures the Valsalva ratio (which incorporates cardiac parasympathetic and sympathetic nervous system activity3) was a strong predictor of myocardial ischemia (which may be silent). The study by Young et al reported results of change in heart rate from lying to standing, indicating that the presence of cardiac autonomic dysfunction had one of the highest hazard ratios associated with the primary events, greater than many of the other clinical factors. In addition, numbness and absence of sensation, which are indices of peripheral neuropathy, had hazard ratios of 2.23 and 2.83, respectively (P < .05 for both). It therefore seems that greater attention to autonomic function should be considered.