Surface electrocardiography (ECG) criteria can be used to discriminate post-septal right ventricular (RV) pacing cardiac memory (CM) from myocardial ischemia with high sensitivity and specificity, according to study results published in the Journal of Electrocardiography.
In this study designed to find ECG criteria for discriminating post-septal pacing CM from ischemia T wave inversions, researchers analyzed 2 groups of patients: a CM group with dual-chamber pacemakers for bradycardia-tachycardia syndrome or sinus node dysfunction (n=23) and an ischemia group (IS) with acute ischemia T wave changes in non-ST elevation acute coronary syndrome who underwent coronary angiography (n=26). The CM group study protocol consisted of 5 visits, in which CM was induced by 2 weeks of pacing in DDD mode with short AV interval; researchers confirmed ventricular pacing for >95% of the time by pacemaker interrogation. The IS group study protocol consisted of a single visit to collect detailed history and clinical examination and evaluation of current medications, baseline blood tests, and ECGs showing the maximal T wave inversion.
After 1 week of pacing in the CM group, the T wave axis changed significantly from the baseline assessment before pacing (P <.001). At peak CM, the T wave axis showed the most important deviation from baseline, similar to the value of the paced QRS axis (peak T wave axis=75.8±18.5 degrees; paced QRS axis=82.7±30.1 degrees; r=0.63). At the fourth visit, the difference in T wave axis from baseline remained significant (P =.02), but at the final visit, T wave axis was similar to baseline (P =.48). Compared with right coronary artery (RCA)/circumflex artery (Cx) ischemia, T wave axis changes in the frontal plane; all CM patients had positive T waves in aVF, while none of the RCA or Cx patients had this feature.
Also, CM could not be differentiated from left anterior descending artery (LAD) ischemia based on T wave axis in the frontal plane. When researchers analyzed the T wave in the transversal vs frontal plane, T wave amplitude in aVF was ≥ the absolute value of the more negative T wave in the precordial leads for 15 of the 23 patients in the CM group and 1 of the 17 patients in the LAD group (P <.001). The final criteria also included positive T in V5 and positive or isoelectric T in lead I, which discriminated CM patients from all ischemia patients with a sensitivity of 91% (95% CI, 72%-99%) and specificity of 92% (95% CI, 75%-99%).
This study was limited by the relatively low number of patients, which was a consequence of attempting to use strict inclusion and exclusion ECG criteria. This makes subgroup analysis by culprit vessel more difficult. These conclusions do not apply to patients with other causes of T wave abnormalities. Exclusion of myocardial ischemia in the CM group was done by performing a stress test because the researchers could not ethically justify invasive coronary angiography without clinical indication.
“Our study showed that post-septal RV pacing cardiac memory was visible on the ECG after 1 week of >95% ventricular pacing, started to disappear in <1 week after pacing cessation, and was completely reversible within 4 weeks of pacing cessation,” the researchers concluded. “This relatively simple ECG algorithm could be used in clinical practice, including emergency room scenarios, in addition to the other guideline recommendations, for better discrimination between myocardial ischemia and a benign condition.”
Suran M-C-B, Margulescu A-D, Bruja R, Siliste C, Vinereanu D. Surface ECG criteria can discriminate post-septal pacing cardiac memory from ischemic T wave inversions. J Electrocardiol. 2020;58:10-17.