Progression towards heart failure after myocardial infarction is accompanied by a change in the spatial QRS-T angle

Myocardial infarction (MI) is a major risk factor for heart failure (HF). The ECG is known to change during the acute and the healing phases of MI, and it stabilizes in the chronic phase. We expect that further ECG changes in the chronic period actually signify a worsening clinical condition / emergence of HF. One major characteristic that signifies an ECG change is the spatial QRS-T angle (SA). It is generally believed that a worsening ECG is accompanied by an enlargement of SA, but we have seen that some patients who developed HF after MI showed a decrease of SA. In the current study we aim to demonstrate that development of HF after MI is accompanied by a change in SA, but irrespective its sign. We retrospectively studied 81 control patients (67/14 male/female, mean±SD age 64±10 years) and 48 cases (38/10 male/female mean±SD age 60±12 years). Control patients had a healed MI and had, thereafter, two elective ECGs (baseline and follow-up) made >1 year apart. Case patients had a healed MI but presented later at our HF outpatient clinic with HF symptoms. Their baseline ECG was made at least 6 months post MI; the ECG made when presenting at the HF outpatient clinic was called follow-up ECG. In each ECG, we computed SA, and in each patient we computed the difference between the baseline and follow-up SAs. Finally we performed a ROC analysis on the signed and unsigned individual SA differences. ROC analysis revealed an area-under-the-curve (AUC) of 0.71 for signed SA differences, and 0.78 for unsigned SA differences. Both AUCs were significantly larger than 0.5, but the difference between these two curves did not reach statistical significance. In conclusion our study suggests that the best case-control separation can be attained by considering absolute SA changes, but a larger study is needed to demonstrate that SA changes irrespective the sign are performing significantly better than signed SA changes. The absolute change in SA is a promising ECG feature to detect emerging HF in post-MI patients.