Transient myocardial ischaemia: new questions about autonomic responses.

In this issue of the Journal Manfrini et al., demonstrate that radically different autonomic profiles accompany episodes of spontaneous myocardial ischaemia compared to myocardial ischaemia in the same patient. Practicing cardiologists have known for decades that the location of myocardial ischaemia determines the pattern of autonomic response. For example, acute transmural anterior wall myocardial infarction is often accompanied by sympathetic activation, sinus tachycardia, and relative hypertension, while inferior wall infarction is accompanied by sinus bradycardia and hypotension. Given that heart rate variability is assumed to shed insight into the balance between vagal and sympathetic tone, this led to a number of animal and clinical studies of heart rate variability during myocardial ischaemia. Manfrini et al., now use this method to show that not only the location of ischaemia but also the mechanism of coronary artery occlusion determines the heart rate variability response. They report that ischaemia that occurs apparently spontaneously is accompanied by heart rate variability changes thought to reflect sympathetic dominance, while ischaemia induced by balloon angioplasty of the left anterior descending artery is accompanied by heart rate variability changes thought to accompany parasympathetic dominance.