A previously asymptomatic 20-year-old woman with no family history of sudden cardiac death or cardiovascular risk factors was admitted to our department because of a successfully resuscitated out-of-hospital cardiac arrest. The patient suddenly collapsed at home in front of her brother, who immediately started the cardiopulmonary resuscitation until the arrival of emergency medical services. An automated external defibrillator detected ventricular fibrillation rhythm and, after one shock, the patient returned to spontaneous circulation (total time to the return of spontaneous circulation was 26 min). She was then intubated and transported to our hospital.
The patient’s haemodynamics remained stable without vasopressor administration and an arterial blood gas demonstrated adequate tissue perfusion (lactates levels <2 mmol/L). Electrocardiogram (ECG) showed sinus rhythm with inferolateral inverted T waves and ventricular bigeminy (Panel A). Laboratory exams exhibited normal electrolyte blood levels, negative toxicological screening, no signs of organ damage, and mild elevation of cardiac biomarkers [high-sensitivity cardiac-Troponin-I 421 ng/L, normal values (n.v.) <20 ng/L, myoglobin 253 ng/mL, n.v. <106 ng/mL, creatine kinase-MB 27 U/L, n.v. <20 U/L], without regional wall motion abnormalities suggestive of myocardial ischaemia or infarction. The patient was extubated after 24 h without neurological sequelae.
Echocardiography revealed a myxomatous mitral valve with prolapse and mild regurgitation (Panels B and C and Video 1). Cardiac magnetic resonance showed normal biventricular volumes, wall motion, and function (Video 2) and spotted mitral annulus disjunction (Panels D and E, arrows). Increased native T1 and non-ischaemic late gadolinium enhancement with mid-wall distribution were noted in the basal inferolateral wall (Panels F and G, respectively), in keeping with myocardial fibrosis in the context of mitral valve prolapse/annulus disjunction. In view of the low likelihood of coronary artery disease, coronary angiography was not performed.
A subcutaneous implantable cardioverter-defibrillator (ICD) was placed. Because of a transient QT interval prolongation and the occurrence of frequent ventricular ectopic beats (VEBs) and non-sustained ventricular tachycardias at ECG monitoring during patient sedation and intubation, propranolol 40 mg three times daily was initially started. A genetic study excluded mutations causing Long QT syndrome and only found a CACNA2D1 missense mutation of uncertain clinical significance. However, after 72 h of ECG monitoring free from ventricular arrhythmias or pauses, the patient suddenly experienced a sinus arrest without ventricular escape (Panel H). The asystole lasted 30 s and reverted after external cardiac massage and atropine administration (Panel I). The subcutaneous ICD was therefore replaced by a single-chamber transvenous ICD. Beta-blockers were initially stopped. However, due to a relapse of frequent VEBs and non-sustained ventricular tachycardia, propranolol 40 mg three times daily was restarted, in combination with mexiletine 200 mg twice daily to effectively reduce the burden of ventricular arrhythmias.
The patient was asymptomatic during the remaining hospitalization and was discharged without changes in propanol and mexiletine dosages. At 3-month ICD interrogation, there were neither sustained arrhythmias nor pacing therapy.
Larger case-series and experimental studies are warranted to (i) identify mechanisms and predictors of bradyarrhythmia in patients with mitral valve prolapse and (ii) refine pharmacological and interventional strategies to prevent arrhythmic complications.
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Conflict of interest: None declared.
Funding: None declared.