Effect of increased left ventricle mass on ischemia assessment in electrocardiographic signals: rabbit isolated heart study
Abstract
Detailed quantitative analysis of the effect of left ventricle (LV) hypertrophy on myocardial ischemia (MI) manifestation in ECG is still missing. In this study, rabbit isolated hearts with spontaneously increased LV mass were used to evaluate the effect of such LV alteration on ischemia detection kriteria.
Methods: Electrophysiological effects of increased LV mass were evaluated on rabbit isolated hearts under non-ischemic and ischemic conditions by analysis of various electrogram (EG) parameters. To reveal hearts with increased LV mass, LV weight/heart weight ratio was proposed.
Standard paired and unpaired statistical tests and receiver operating characteristics analysis were used to compare data derived from different groups of animals, monitor EG parameters during global ischemia and evaluate their ability to detect ischemic state. Results: Successful evaluation of both increased LV mass and ischemia is lead-dependent.
Particularly, maximal deviation of QRS and area under QRS associated with anterolateral wall respond significantly to even early phase (the 1st-3rd min) of ischemia. Besides ischemia, these parameters reflect increased LV mass as well (sensitivity approx. 80%).
However, the sensitivity of the parameters to both phenomena may lead to misinterpretations, when inappropriate criteria are selected. Particularly, use of cut-off-based criteria defined from control group for ischemia detection in hearts with increased LV mass may result in dramatic reduction (approx. 15%) of detection specificity due to increased number of false positives.
Nevertheless, criteria adjusted to particular experimental group allow achieving ischemia detection sensitivity of 89-100% and specificity of 94-100%, respectively. Conclusions: It was shown that response of the heart to MI can be successfully evaluated only considering heart-related factors (LV mass) and other methodological aspects (recording electrodes position, selected EG parameters, cut-off criteria, etc.).