Suspected myocardial infarction and left bundle branch block: electrocardiographic indicators of acute ischaemia.

Abstract

Objectives-To examine the use of thrombolytic treatment in patients with suspected acute myocardial infarction (AMI) and left bundle branch block (LBBB). To evaluate electrocardiographic criteria for the identification of AMI in the presence of LBBB, and examine the implications of using these criteria in the clinical setting. Methods-A retrospective study over two years, based in two Sheffield teaching hospitals. Patients presenting with LBBB and suspected AMI were studied by analysis of an AMI database. The proportion of patients with LBBB and AMI receiving thrombolysis, and the in-hospital delay before the start of treatment, were used as indicators of current performance.Three predictive criteria were applied to the electrocardiograms (ECGs) retrospectively, and their ability to identify acute ischaemic change assessed. The implications of using the predictive criteria in the clinical setting were explored.Result-Twenty three per cent (5122) of patients with LBBB and AMI did not receive thrombolysis, in the absence of documented contraindications. The mean in-hospital treatment delay for thrombolysed patients was 154 minutes. Forty eight per cent (16/33) of those thrombolysed did not have a final clinical diagnosis of AMI. In the majority of cases (8/12), the decision not to administer thrombolysis was based on a single ECG recording.The presence of any of the predictive electrocardiographic criteria was associated with a diagnosis ofAMI, with a sensitivity of 0.79 (95% confidence interval 0.63 to 0.95), specificity 1, positive predictive value 1, and negative predictive value 0.79. The K scores between four independent observers showed either substantial or near perfect agreement.

Electrocardiographic Diagnosis of Myocardial Infarction during Left Bundle Branch Block

“…The clinical utility of the criteria and scoring system of Sgarbossa and colleagues [1] have been validated by other studies, all of which have also demonstrated a high specificity, but some have shown an even lower sensitivity than the original data of Sgarbossa and colleagues [1] in terms of the three individual ST-segment criteria and the scoring algorithm [8,[16][17][18][19][20][21]. As such, although the criteria and the algorithm cannot be used to rule out MI, it can help to rule it in.…”

T Vector and Loop Characteristics Improve Detection of Myocardial Injury After Infarction

“…Bär et al [17] QRS duration (ms) Michelle et al [18] Left bundle branch block (0 = normal, 1 = left bundle branch block) Edhouse et al [19] the curve and the baseline from QRS end (J point) to T end in X, Y, and Z Frank leads, respectively. Considering the sample values of the T loop as mass points, the matrix of inertia can be defined.…”

“…The ECG recordings were manually analyzed with an ECG ruler by an experienced cardiologist. Table 1 lists the infarct indicators of the standard 12-lead ECG [14][15][16][17][18][19].…”

ECG Patterns Confounding the ECG Diagnosis of Acute Coronary Syndrome: Left Bundle Branch Block, Right Ventricular Paced Rhythms, and Left Ventricular Hypertrophy

“…These criteria reflect the presence of tall, left precordial R waves (I, aVL, V5, and V6) and deep, right precordial S waves (V1 and V2), consistent with the increased left ventricular mass and close proximity to the anterior chest wall (Figs. [13][14][15][16]. LVH is also associated with poor R-wave progression and the presence of a QS pattern (no R wave) in leads V1 and V2 (rarely beyond lead V3).…”

“…In this study, all patients who do not experience AMI had clinical prediction rule scores not suggestive of AMI; approximately 80% of those patients who experience biochemically proven AMI had scores supporting the diagnosis of AMI. The researchers concluded that the diagnosis of AMI in the chest-pain patient who has developed LBBB is difficult yet noted that the clinical decision rule was useful in the suspected AMI patient who has developed LBBB [13].…”