To the Editor:—
I read with great interest the article by Karpati et al. 1documenting the high incidence of myocardial ischemia in parturients with significant postpartum hemorrhage. This is the second report that clearly documents the occurrence of myocardial ischemia in this population of young, otherwise healthy women with “normal” coronary arteries. In 2001, Moran et al. 2used the newly available marker, myocardial troponin I, to definitively correlate electrocardiogram changes during cesarean section with myocardial ischemia. It is interesting to reflect how much views have changed during the past 15 yr.
In 1990, we published a series regarding the incidence of electrocardiographic changes during cesarean delivery.3At that time, our hypothesis that parturients could experience ischemia solely on the basis of an imbalance of myocardial oxygen supply and demand was met with almost universal derision. Numerous other investigators subsequently confirmed a significant incidence of electrocardiographic changes,4–7but of these, only Mathew et al. 4conceded that myocardial ischemia might be a possible cause. There was tremendous resistance to the idea that ischemia could be induced in someone with “clean” coronary arteries, despite the fact that in every other setting, such electrocardiogram changes would be considered ischemia until proven otherwise. Almost any other explanation was considered more likely—neurocirculatory asthenia, vasoregulatory asthenia, hyperdynamic heart syndrome, mitral valve prolapse, autonomic system imbalance, cardiac sympathetic block, and epinephrine.4,7
Now, Karpati et al. 1can unabashedly state, “Our study … showed that myocardial ischemia was probably related to a significant alteration in the myocardial supply–demand ratio in parturients with otherwise ‘normal’ coronary arteries … myocardial oxygen supply was impaired by lowered arterial blood pressure, whereas increased heart rate resulted in an increased myocardial oxygen demand.” Not surprisingly, their findings of decreased blood pressure and increased heart rate mirror the findings in our 1990 series (table 5 in Palmer et al. 3).
Although it is nice to be have our original hypothesis validated after all these years, it also serves to prove the old adage: When you hear hoofbeats (in this case, chest pain, shortness of breath, and electrocardiogram changes), think horses, not zebras.
University of Arizona Health Sciences Center, Tucson, Arizona. firstname.lastname@example.org