Israel Medical Association Journal

Abstract

Background: Heart rate variability (HRV) analysis has been shown to be a predictor of sudden cardiac death and all-cause mortality in patients with cardiac disease.

Objectives: To examine whether newer HRV analysis algorithms, as used by the HeartTrends device, are superior to exercise stress testing (EST) for the detection of myocardial ischemia in patients without known coronary artery disease (CAD).

Methods: We present pilot data of the first 100 subjects enrolled in a clinical trial designed to evaluate the yield of short-term (1 hour) HRV testing for the detection of myocardial ischemia. The study population comprised subjects without known CAD referred to a tertiary medical center for EST with single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). All patients underwent a 1 hour electrocardiographic acquisition for HRV analysis with a HeartTrends device prior to EST with MPI. Sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) were calculated for EST and HRV analysis, using MPI as the gold standard for the non-invasive detection of myocardial ischemia.

Results: In this cohort 15% had a pathologic MPI result. HRV analysis showed superior sensitivity (85%), PPV (50%) and NPV (97%) as compared to standard EST (53%, 42%, 90%, respectively), while the specificity of the two tests was similar (86% and 85%, respectively). The close agreement between HRV and MPI was even more pronounced among patients > 65 years of age.

Conclusions: Our pilot data suggest that the diagnostic yield of the novel HeartTrends HRV algorithm is superior to conventional EST for the non-invasive detection of myocardial ischemia.

Background: Electrocardiography has a very low sensitivity in detecting dobutamine-induced myocardial ischemia.

Objectives: To assess the added diagnostic value of a new cardiac performance index (dP/dt^ejc) measurement, based on brachial artery flow changes, as compared to standard 12-lead ECG, for detecting dobutamine-nduced myocardial ischemia, using Tc99m-Sestamibi single-photon emission computed tomography as the gold standard of comparison to assess the presence or absence of ischemia.

Methods: The study group comprised 40 patients undergoing Sestamibi-SPECT[1]/dobutamine stress test. Simultaneous measurements of ECG and brachial artery dP/dt^ejc were performed at each dobutamine level. In 19 of the 40 patients perfusion defects compatible with ischemia were detected on SPECT. The increase in dP/dt^ejc during infusion of dobutamine in this group was severely impaired as compared to the non-ischemic group. dP/dt^ejc outcome was combined with the ECG results, giving an ECG-enhanced value, and compared to ECG alone.

Results: The sensitivity improved dramatically from 16% to 79%, positive predictive value increased from 60% to 68% and negative predictive value from 54% to 78%, and specificity decreased from 90% to 67%.
Conclusions: If ECG alone is used for specificity, the combination with dP/dt^ejc improved the sensitivity of the test and could be a cost-savings alternative to cardiac imaging or perfusion studies to detect myocardial ischemia, especially in patients unable to exercise