High degree Atrioventricular block in patients with acute inferior Myocardial Infarction with and without Right Ventricular involvement.

Objective: To determine the influence of time on development of high degree Atrioventricular (AV) block in patients with inferior Myocardial Infarction (MI), its association with Right Ventricular (RV) infarction and its ultimate morbidity and mortality.

Study Design: A descriptive study.

Place And Duration Of Study: The Emergency Department (ED) and the units of adult cardiology at National Institute of Cardiovascular Diseases (NICVD), Karachi, from October 2006 to March 2007.

Methodology: Patients presented at ED with typical chest pain and subsequently diagnosed by standardized diagnostic criteria as having inferior MI were recruited prospectively. Patients were first analyzed on the basis of absence (Group A) or presence (Group B) of high degree AV block regardless of RV infarction. Then after patients were divided into two groups, those without RV infarction (Group I) and with RV infarction (Group II). Each group was further sub-divided as Ia, IIa and Ib, IIb depending on absence or presence of high degree AV block respectively. Each group was analyzed for comparisons with different variables for prediction of influence of time, proportion of RV infarction, association of AV block with RV infarction, complication profile and inmortality.

Results: Of the 220 patients with inferior MI, 52 (23.6%) had high degree AV block and 83 (37.7%) had RV infarction. They were older in age (p< 0.003). Patients who took more time to seek medical treatment from onset of symptoms were more prone to develop AV block (p<0.001). Among patients with block, 73% received thrombolytic therapy (p<0.009) and temporary pacemaker (TPM) was implanted in 75% (p<0.0001). Mortality was significantly high in those patients (p<0.0001). In group II, 61.4% presented with sinus rhythm (p<0.001). TPM was implanted to 31.3% (p<0.0001). In the 4 days of hospital course, 8.4% of patients with RV infarction developed AV block (p<0.005), whereas 10.8% of patients without RV infarction experienced post MI angina (p<0.031). Mortality was found significantly high when block was associated with RV infarction (p<0.007). No significant difference was found in response to atropine, volume replacement or streptokinase administration and reverting of block to sinus rhythm.

Conclusion: Patients with inferior MI who took more time to seek medical treatment were found to be more prone to develop high degree AV block. RV infarction was found in about 38% of patients defined a high risk subgroup. High degree AV block significantly influenced the outcome when associated with RV infarction, leading to high mortality.