Background: Conventional exercise stress testing (EST) is limited in its ability to detect myocardial ischemia in patients without known coronary heart disease (CHD), thus mandating a more complex functional evaluation at a significant cost. Heart rate variability (HRV) analysis has been shown to be a predictor of all-cause mortality and sudden cardiac death. We hypothesized that newer HRV analysis algorithms, as used by the HeartTrends device, may be superior to EST for the detection of myocardial ischemia in patients without known CHD.
Methods: We report data of the first 378 prospectively enrolled consecutive patients without known CHD referred to the Sheba Nuclear Cardiology Center for EST with SPECT myocardial perfusion imaging (MPI). All patients underwent a one-hour ECG acquisition for HRV analysis with a HeartTrends device prior to EST with MPI. Sensitivity,specificity, positive and negative predictive values (PPV and NPV, respectively) were calculated for EST and HRV analysis, using MPI as the gold-standard for the noninvasive detection of myocardial ischemia. The study was approved by the local Helsinki Committee and all patients gave written informed consent.
Results: The average cohort's age was 61 (±10) years. 63% were males. 51% had hypertension, 66% had dyslipidemia, 25% had diabetes mellitus, and 45% had a family history of CHD. In this cohort, 15% had a pathologic MPI result. The sensitivity of HRV for detecting myocardial ischemia was 79% as compared with only 29% shown for standard EST (Table). Furthermore, multivariate analysis showed that the HRV was associated with a relative incremental value of 4.8 (p<0.001) as compared with standard EST.
Our data from a prospective clinical trial suggest that the novel HeartTrends HRV algorithm may be useful for the noninvasive detection of myocardial ischemia in patients without known CHD.
