Ronald H. Selvester

The ECG: QRS Change

Known and measured cardiac and torso anatomy, electrophysiology, and resistivities have been incorporated into a three-dimensional propagation model of ventricular excitation [1]. This model includes all the first-order effects known to influence the ECG in man. It has been used to generate QRS criteria for the 12-lead ECG in order to locate infarcts in 12 segments of the left ventricle and to predict the amount of infarct in each segment [2, 3]. The ability of these criteria to predict the size of infarct in each of the three main coronary artery distributions is the subject of this chapter.

Significance of ST-segment depression with R-wave amplitude decrease on exercise testing.

A retrospective evaluation was performed of patients who underwent exercise tests and angiography and 50 ambulatory normal subjects who underwent only exercise testing. We found that when deltaST depression of 0.5 mm was combined with deltaR-wave decrease of 1 mm, the sensitivity and specificity were improved.

Enhanced recognition of ischemia by three variable analysis of the exercise stress test

BACKGROUNDnECG ST-segment deviations have been the standard measure of coronary artery disease (CAD) during the exercise stress test (EST). Our past research has shown other ECG variables to be significant in EST. This study evaluates the benefit of routinely combining these variables in the detection of CAD.nnnMETHODSnSequential patients (n = 439) with suspected CAD referred for EST had their cases reviewed. Clinical and ECG variables were associated with myocardial perfusion imaging (MPI) scintigrams used to detect ischemia during maximum EST.nnnRESULTSnAn increase in P-wave duration was the most sensitive predictor of ischemia with a sensitivity of 64.3%, a specificity of 86.5%, and a positive predictive power (PPP) of 57.8%. ST elevation ≥ 1 mm in lead AVR had a sensitivity of 53.1%, a specificity of 78.3%, and a PPP of 41.3%. ST depression ≥ 1 mm in leads V₄-V₆ had a sensitivity of 11.2%, a specificity of 94.7%, and a PPP of 37.9%. When these variables were combined, specificity and PPP increased to 100% (p < 0.001).nnnCONCLUSIONSnEST evaluation solely by ST deviation fails to identify a significant portion of ischemic cases. Combinations of ΔPWD, ST elevation in AVR, and ST depression improved the identification of ischemia.

Agreement between cardiologists and fellows in interpretation of ischemic electrocardiographic changes in acute myocardial infarction.

BACKGROUNDnTime from symptom onset may not be the best indicator for choosing reperfusion therapy for patients presenting with acute ST-elevation myocardial infarction (STEMI); consequently ECG-based methods have been developed.nnnMETHODSnThis study evaluated the inter-observer agreement between experienced cardiologists and junior doctors in identifying the ECG findings of the pre-infarction syndrome (PIS) and evolving myocardial infarction (EMI). The ECGs of 353 STEMI patients were independently analyzed by two cardiologists, one fellow in cardiology, one fellow in internal medicine and a medical student. The last two were given a half-hour introduction of the PIS/EMI-algorithm.nnnRESULTSnThe inter-observer reliability between all the investigators was found to be good according to kappa statistics (κ 0.632-0.790) for the whole study population. When divided into different subgroups, the inter-observer agreements were from good to very good between the cardiologists and the fellow in cardiology (κ 0.652 -0.813) and from moderate to good (κ 0.464-0.784) between the fellow in internal medicine, medical student and the others.nnnCONCLUSIONSnThe PIS and EMI ECG patterns are reliably identified by experienced cardiologists and can be easily adopted by junior doctors.