Out-of-hospital cardiac arrest in a mitral valve prolapse young male patient with acute mitral regurgitation due to cordal rupture. A case with a literature review

Athanassios Antonopoulos (1) MD, PhD, FESC, Simona Postorivo (2) MD, Raffaella Francesconi (2) MD, Elisabetta Varani (1) MD
1) Department of Cardiology, Ospedale per gli Infermi, Faenza (RA), AUSL Romagna, Italy.
2) Emergency Medicine, Ospedale per gli Infermi, Faenza (RA), AUSL Romagna, Italy.

Introduction

Mitral valve prolapse (MVP) has been reported as a relatively common finding in the general population (1,2). Patients with relatively non-specific symptoms such as palpitations and atypical chest pain who are found to have MVP, continue to represent a major clinical conundrum for the practicing cardiologist (3). Cardiac arrhythmias and/or cardiac death is an underappreciated issue in MVP patients. When tested with Holter electrocardiogram (ECG) monitoring, MVP patients had a prevalence of ventricular arrhythmias as high as 34%, with premature ventricular contractions as the most common pattern (66% of the cases) (4). Anders et al presented a case series which suggest that even clinically benign cases of MVP in young adults might result in sudden unexpected death (5). In spite of that, cardiac arrest and arrhythmic sudden cardiac death (SCD) in patients with MVP based on the data of a community study are rare (6). In the present case we describe a patient with an out-of-hospital cardiac arrest due to ventricular fibrillation as the first manifestation of MVP.

Case Report

A 33-year-old male had an out-of-hospital sudden cardiac arrest in a restaurant during lunch without foreign body obstruction. Friends who were together with him called the ambulance, which arrived 7 minutes later and started a first cardiac massage. Upon the arrival of the medical service, the initial observed cardiac rhythm was ventricular fibrillation (figure 1).
Figure 1: The initial cardiac rhythm: ventricular fibrillation

Cardiopulmonary resuscitation was immediately started and continued for 15 minutes (three DC defibrillation 200 Joules for ventricular fibrillation, one synchronized cardioversion 150 Joules for ventricular tachycardia with pulse and a short period of pulseless electrical activity treated with cardiac massage and epinephrine) before returning in spontaneous circulation with sinus tachycardia. During that time, attempts for endotracheal intubation failed, despite continuous suction applied, due a lot of regurgitated food. The patient in coma state (Glasgow coma scale 4) was treated with intravenous sedation to support ventilation with supraglottic tube. The patient was then transported by ambulance to the emergency department of the nearest available hospital for further assistance. Endotracheal intubation was finally obtained and completed with fiberoptic bronchoscopy toilette. Chest x-ray showed ab ingestis pneumonia. Body temperature was normal. Initial blood investigations were as follow: pH 7.026, PCO2 82.9 mmHg, PO2 73.9 mmHg, BEb -11.8 mmol/L, lactates 2.18 mmol/L, potassium 3.62 mmmol/L, sodium 138 mmol/L, hemoglobin (Hb) 16 g/dL, glucose 320 mg/dL, creatinine 1.32 mg/dL, high sensitivity troponin 192 ng/L. Important mitral regurgitation, probably due to ruptured mitral chordae tendinae, was observed by trans-thoracic echocardiography in the emergency room when the patient arrived. Systolic blood pressure was 60 mmHg and infusion of norepinephrine has been started to increase mean pressure. No changes in repolarization were noticed in the first 12 leads ECG after resuscitation (figure 2) but premature ventricular complexes were observed.

 

Figure 2: The first 12 leads ECG after resuscitation
 
Due to the hemodynamic instability, a cardiac surgeon was contacted. He was immediately transferred to Cardiovascular Surgery Department where initial diagnosis of myxomatous MVP with acute mitral rupture of P2 chordae tendinae and severe mitral regurgitation was confirmed. Cardiac surgery consisted in anterior minithoracotomy after extracorporeal circulation for annuloplasty, with triangular resection of posterior leaflet and implantation of a prosthetic ring. Because of persistent respiratory insufficiency, he was then supported by arterio-venous extracorporeal membrane oxygenation. Head and chest computed tomography was performed and showed an ischemic area in posterior cranial fossa associated with cerebral edema and multiple ab ingestis pulmonary lesions with small bilateral pleural effusion. During the post operation days the presence of premature ventricular complexes were recorded. On the other hand a hemodynamic stability was obtained. Mechanical ventilation was successfully weaned and the trachea was extubated five days after admission. The patient was treated with eight blood transfusions (Hb 8.5→10.5 g/dL), broad spectrum antibiotic therapy (blood culture positive for Hafnia alvei), fluid and diuretic for renal failure (creatinine 3.98→2.56 mg/dL).
Although the patient experienced an initial deficit in short term memory function, he continued in a good neurological recovery. A further inquiry revealed no family history of sudden cardiac death, cardiac disease or connective tissues disorders. An echocardiographic study was performed to the brother and mother of patient and did not revealed any valvular or other structural cardiac pathology. The father was dead because of advanced stage cirrhosis. Patient was discharged from Cardiovascular Surgery Department and transferred in Cardiology Department for further rehabilitation.
 

Follow-up

Patient was followed for a period of two years. He remained in therapy with bisoprolol 1.25 mg and furosemide 25 mg two times daily. Initially he showed dyspnea and shortness of breath for at least one year. The trans-thoracic echocardiography (Figure 3) performed six months after mitral valve repaired showed normal left ventricular dimensions with a moderate mitral insufficiency and high pulmonary pressure at rest (45 mmHg). Surface electrocardiogram did not display any repolarization changes like QT prolongation, inverted or biphasic T waves or T wave alternans. Moreover, a Holter ECG performed in the same period demonstrated frequent ventricular extrasystolic beats, isolated but also complex, like couples and non-sustained run of ventricular tachycardia (max 4 complexes). Blood tests were normal in Hb, renal function and potassium levels. Based on the above findings, we decided to increase diuretic therapy by adding 25 mg of spironolactone. One year later an other clinical, echocardiographic and Holter ECG was performed. Patient symptoms did not present an important improvement. Pulmonary pressure remained more or less around the same value with normal left ventricular dimensions and a moderate mitral insufficiency. Holter ECG showed significant reduction of the premature ventricular complexes. Blood tests remained into normal levels. A third cardiac control, six months later, has revealed a clear improvement of symptoms with mitral insufficiency reduced to insignificant and pulmonary pressure to 12 mmHg (Figure 4), Holter ECG showed a normal sinus rhythm (55-75 beats per minute) without any extrasystole.
 

Figure 3: Mitral insufficiency six months after mitral valve repair

Figure 4: Mitral insufficiency during last cardiology visit, two years after mitral valve repair

Discussion

Till now, the presence of ventricular arrhythmias among patients with MVP has been underappreciated. Some previous studies described an increased incidence of serious ventricular arrhythmias in this kind of patients. On the contrary, other studies demonstrated that occurrence of MVP, among sudden cardiac arrest causes in the community, may not be significantly increased from what is expected in the general population (2, 6). This rare case regards a young male with asymptomatic MVP who was resuscitated from out-of-hospital sudden cardiac arrest. The exact mechanism linking MVP to sudden cardiac arrest is still not known. An autoptic study in patients with MVP had shown that mitral valve leaflet length and posterior leaflet thickness were greater in hearts of patients who died suddenly compared to patients with MVP who died from other causes (7).
Until now the debate continues as to whether MVP is the cause of SCD or merely an association. However, several possibilities have been advanced. Previous studies supposed the hypothesis of an abnormal autonomic and hyperadrenergic state (8). Boudoulas et al (9) demonstrated that patients with MVP had frequent, transient and inappropriate increases of catecholamines during the day or stressful activities. The above condition may produce transient QT prolongation relative to the QS2 interval (electromechanical systole). To further support this hypothesis another study showed that 24-hour catecholamines excretion and frequency of premature ventricular beats were parallel (10). Wilde and colleagues (11) performed detailed mapping studies on a patient with MVP and ventricular tachycardia and concluded that delayed afterdepolarization-induced triggered activity was the mechanism, with stretch and fibrosis of the papillary muscles, contributing to the origin of the arrhythmia.
Furthermore, some studies have suggested that ventricular arrhythmias may be more frequent in MVP when mitral regurgitation is present (12,13,14). This could reflect hemodynamic consequences of volume overload; however it is noteworthy that the mean left ventricular ejection fraction was normal and left ventricular diameter not significantly increased in the MVP patients compared to the cases without MVP in our population. Additionally, it has been proposed that a subset of young patients with isolated MVP and SCD could actually have less mitral regurgitation (15,16). Certain studies have found women to be at higher risk (4, 14) that not regards our patient. An other study, using signal-averaged ECG, identified an increased frequency of late potentials in MVP patients (17); however the utility of this tool in risk prediction is unclear.
The arrhythmic substrate in this setting of patients was also recently investigated by Basso and colleagues (18), who found that in patients who experienced sudden cardiac death with MVP was present fibrosis in the papillary muscles of adjacent free wall and infero-basal wall, as demonstrated by late gadolinium-enhancement on magnetic resonance study. The above features closely overlapping with the histopathological findings which described that kind of fibrosis pattern different in terms of type (i.e. scarring) and location (i.e. papillary muscles and basal potero-lateral wall). Moreover, the degree of MVP and leaflets thickness was found to be related with QT dispersion, providing also a mechanical correlation for electrical disturbances in this subset of patients (19). In a similar way, Sriram et al studying patients with out-of-hospital cardiac arrest in bileaflet mitral valve prolapsed syndrome, found on the electrophysiological study that the earliest site of origin of premature ventricular complexes was mapped to the tips, body or bases of either the anterior or posterior papillary muscles (20). Additionally, it is worth to underline that human mitral valve has distinct patterns of innervation. Mechanical stimuli produced by irregular coaptation of prolapsed mitral cups may cause an abnormal autonomic nerve feedback between the central nervous system and the mitral valve (21).
In our case we did not have the possibility of MRI investigation due to the emergency situation and the electrocardiographic evaluation after resuscitation was in sinus rhythm without significant repolarization changes. Moreover, the explanation of the genesis of ventricular fibrillation in our patient is not clear. We hypothesed that a mechanical stimulation, with an important papillary stretch and the sudden rupture of cordae tendinee, could cause an abnormal nerve feedback between central nervous system and mitral cusps. This is of relevance in most of the previous studies demonstrating the importance of papillary muscle-annular continuity in the maintenance of normal ventricular function after surgical valve correction (12). Consequently, an urgent surgical correction of the above described mechanism as first line therapeutic option, may treat also the arrhythmogenic substrate.

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