Asystole Following Nitroglycerin: A Review of Two Cases
Case 2
The patient in Case 2, had chest pain upon arrival at the ED and was administered SL NTG, with notable improvement in chest pain, but not complete resolution. With serial examinations, including a review of pain scale scores, she was given two subsequent doses of SL NTG. Within 1 minute from receiving the third dose of NTG, the patient complained of lightheadedness and nausea, and became pale and diaphoretic. Telemetry revealed bradycardia, which progressed to junctional escape beats, followed by ventricular escape beats, and then asystole, at which point she became unresponsive and pulseless. Cardiopulmonary resuscitation was initiated, with a return of spontaneous circulation within 15 seconds of intervention; she gradually returned to her baseline with observation. Repeat vital signs were: BP, 155/70 mm Hg; HR, 99 beats/min; RR, 20 breaths/min; and she was afebrile. Oxygen saturation was 99% on 15 liters of oxygen/min, which was weaned prior to hospital admission. A repeat ECG demonstrated a normal sinus rhythm without evidence of ischemia. Cardiology service was consulted and the patient was admitted for further evaluation, including a 3-day inpatient observation, serial cardiac enzymes, thyroid panel, contrast chest computed tomography scan, echocardiogram, and cardiac stress test. All studies were within normal limits, except for an incidental minor pectus excavatum attributed to the quality CPR. In addition, a nuclear medicine perfusion imaging study was obtained, which revealed no evidence of myocardial ischemia or scar, consistent with the patient’s stable course. The patient’s symptoms resolved early in her inpatient stay, and she was discharged home with prescriptions for antihypertensive and antihyperlipidemia agents and instructed to follow-up with her primary care physician.
Discussion
Nitroglycerin is commonly used to treat various symptoms of cardiac origin, namely relief of chest pain due to suspected acute coronary syndromes.2,3The mechanism of action of NTG is predominantly through potent smooth muscle relaxation of the venous and arterial systems, reducing both preload and afterload.2,3 This results in reduced myocardial oxygen demand, potentiating the relief of myocardial ischemia.
Contraindications
Contraindications to NTG include known allergy, pericardial tamponade, restrictive cardiomyopathy, increased intracranial pressure, and concomitant use of phosphodiesterase inhibitors. Moreover, NTG should not be given to treat conditions wherein cardiac output is dependent on venous return, as in the setting of inferior myocardial infarction (MI) with right ventricular involvement. Furthermore, there is no evidence in the literature to support the erroneous use of NTG as a diagnostic therapy, with limited sensitivity yields for conclusive cardiac-associated chest pain.8
Adverse Effects and Events
The common side effects of NTG are well documented and include hypotension, tachycardia, flushing, nausea, vomiting, and headache.7,3,6 Syncope, bradycardia, and cardiac arrest following the administration of NTG are rare events, as evidenced by the paucity of literature describing these complications. Rather, it appears that these side effects are observed only in the setting of myocardial ischemia or MI.3,9-11 Fewer cases of ventricular fibrillation, responsive to defibrillation, and asystole also have been observed.9The exact mechanism for bradycardia without hypotension and subsequent asystole following NTG administration remains elusive, though this response is thought to be associated with the Bezold-Jarisch reflex.
