Serial ECG recordings via marked chest wall landmarks: An essential requirement for the diagnosis of myocardial infarction in the presence of left bundle branch block

Detection of acute myocardial infarction (AMI) in the presence of left bundle branch block (LBBB) continues to be problematic, although recently proposed criteria by Sgarbossa et al have contributed considerably in alleviating the diagnostic difficulties. Urgency in making the diagnosis stems from the desire to administer thrombolytic therapy as soon as possible after the patient encounter. The proposed criteria focus on ST-segment deviations, and imply that other parts of the ECG curve do not contribute much to the early diagnosis of AMI. Observations in the daily practice and some previous work suggest that significant alterations in the amplitude of ST-segment deviations are witnessed when variation of the sites of precordial lead recordings, by even 1.0 cm, is implemented. In contrast serial ECG recordings made close in time in patients with AMI are remarkably reproducible. World-wide experience in electrocardiography has shown that recordings of the precordial leads are made with astonishingly marked neglect as to the employment of the proper chest landmarks. This further compounds the diagnostic difficulty in detecting AMI in the presence of LBBB. It is proposed that ensuring the reproducibility of the recording of the precordial leads (even if the chosen landmarks are not the conventional ones) will enhance the diagnostic sensitivity for the detection of AMI in this setting. Introducing this dynamic aspect in the diagnostic effort (serial ECGs) may enhance the contribution of the static ST-segment criteria focusing on fixed thresholds of deviation amplitudes; also the non ST-segment ECG parts may receive another evaluation as to their contribution to the diagnosis of AMI in the presence of LBBB.