Q-wave versus non-Q wave myocardial infarction: a meaningless distinction.
The whole subject can thus be summed up in two statements. 1. Every appropriately designed study comparing first Q and NQMI's has found no difference in post-MI course of the two categories and no foundation for the common notion that the NQMI is a uniquely "unstable" entity, to be classed with unstable angina in terms of prognosis and management. Nine such studies have been published. On the other hand, all studies alleging the "unstable" character of the NQMI have been invalidated by major flaws, chief among them the comparison of undifferentiated mixtures of first and subsequent infarcts with widely differing mortality and morbidity. This confusion is further compounded by the fact that subsequent infarcts generate Qwaves less than half as often as first infarcts. 2. All current studies indicate that there is no benefit to an invasive as compared with a conservative protocol for management of NQMI. Since the characterization of an infarct as "non-Q' conveys no therapeutic implications, the classification becomes irrelevant and should be discarded. Two quotations sum the whole matter succinctly. Moss (63) commented that "The Q-wave versus non-Q-wave categorization does not provide sufficient sensitivity, specificity, or predictive accuracy about the subsequent clinical course of patients with a first myocardial infarction to use it as reliable data in the clinical decision-making process." Surawicz (64) put the matter even more concisely: ". . . a non-Qwave MI is not a unique entity: rather it is a smaller and less extensive MI." In a word, the magnitude of a myocardial infarction should be judged on anatomical and functional considerations rather than on the designation of Qwave versus non-Qwave infarction.