Asystole Following Nitroglycerin: A Review of Two Cases

Bezold-Jarisch Reflex

The Bezold-Jarisch reflex is a cardiovascular response consisting of bradycardia and hypotension that is believed to be from stimulation of inhibitory cardiac receptors by stretch, chemical, or pharmacological stimulation.¹² The earliest cases of Bezold-Jarisch reflex following NTG occurred in the setting of MI and were attributed to ongoing myocardial ischemia.¹³ Recent studies have revealed that coronary stenosis without concurrent ischemia is actually not a sensitizing factor, and that bradycardia and asystole following NTG have occurred in patients without evidence of coronary artery disease.^9,14 As part of this response, it is theorized that the development of bradycardia is related to vasovagal stimulation, a centrally mediated response to the headache or nausea following NTG administration.^10,11,15

Despite these observational studies and after thorough review of the available cases, no unifying factors exist to predict with certainty the patient population in which this response is likely to occur.^12,16Based on a literature review, it appears that asystole following NTG is self-limited; however, in most cases, bradycardia was treated with atropine without adverse side effects.^12,15,16

Conclusion

The two cases presented involved a middle-aged male patient and an elderly female patient, both of whom had several cardiac risk factors but no evidence of acute ischemia or infarction on ECG or laboratory studies. It is well established that NTG can cause hypotension without bradycardia; however, the development of bradycardia without, or even preceding, hypotension is less recognized. Several mechanisms have been postulated but none fully explain this reaction; moreover, no anticipatory risk factors have been consistently observed. Even though the patients in Case 1 and 2 underwent extensive evaluation, no specific etiology of the observed reaction was identified, though neither patient underwent cardiac catheterization to definitively exclude abnormal coronary artery pathology as a precipitating factor.

These cases illustrate the unpredictable adverse reaction to a common medication used for a ubiquitous complaint. The explanation as to the source for this reaction is lacking, the literature has consistently described the transient and self-limiting effect of asystole following NTG.^9,12,14,16Bradycardia, though self-limiting, remains responsive to appropriately dosed atropine when NTG-induced.^3,12,16 The authors wish to stress the importance of establishing IV access and being prepared for adverse events whenever administering sublingual nitroglycerin to a patient.