• Kian-Keong Poh, Boon-Lock Chia, Huay-Cheem Tan, Tiong-Cheng Yeo, and Yean-Teng Lim.
• Cardiac Department, National University Hospital, Singapore. pohkk@singnet.com
• Int. J. Cardiol. 2004 Dec 1; 97 (3): 389-92.

Background And ObjectiveOcclusion of the circumflex coronary artery may present with either ST elevation typical of inferior or lateral myocardial infarction, ST depression or a normal 12-lead electrocardiogram (ECG). In patients presenting with ST depression, concomitant ST elevation in the posterior leads V7, V8 and V9 is believed to reflect ST-elevation myocardial infarction of the posterior wall. However, to be confident of this diagnosis, it is necessary to know that posterior ST depression does not occur in acute subendocardial ischaemia.Methods And ResultsWe have prospectively recorded leads V7, V8 and V9 simultaneously with the standard 12-lead ECG in patients who underwent treadmill stress test. Group A consists of 35 patients who showed ischaemic praecordial ST depression in their 12-lead ECGs during treadmill stress test and subsequent angiographic documentation of significant coronary artery disease. Group B consists of 35 subjects who showed normal ECG findings during treadmill stress test. In none of the Group A or B patients was there ST elevation in leads V7, V8 or V9 either at rest or at peak exercise. ST depression was seen in 69% in V7, 31% in V8 and 11% in V9 in the Group A patients at peak exercise.ConclusionST elevation in leads V7, V8 and V9 is uncommon in patients presenting with subendocardial ischaemia. Therefore, in patients presenting with acute chest pain and ST depression in the 12-lead ECG, concomitant posterior ST elevation may be a reliable indicator of ST elevation posterior MI. This is likely due to circumflex artery occlusion and may require thrombolytic therapy.

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