Spontaneous Papillary Muscle Rupture: An Uncommon Presentation in the Absence of Myocardial Infarction

Introduction

Papillary muscle rupture (PMR) is a rare complication of myocardial infarction (MI), with an incidence in the United States of 0.029% [1]. It is even more rare when no MI or infective endocarditis is suspected and has a very high in-hospital mortality rate, as it leads to cardiogenic shock [1]. We only found a few published cases of spontaneous PMR [2–4]. Therefore, the purpose of this case report was to highlight the existence and recognition of acute valvular diseases, specifically PMR, to facilitate prompt early workup, particularly TTE, and treatment.

Case Report

A 48-year-old man with a medical history of well-controlled type 2 diabetes mellites visited the ED owing to shortness of breath that had started approximately 5 hours before. According to the emergency medical services, 1 h prior to arrival, his level of consciousness started to decrease. He patient had previously experienced shortness of breath that was not exertional or reproducible, and he had no history of chest trauma, chest pain, syncope, seizure, or fever. He also had no recent history of surgery, extended travelling, or weight loss, nor did he have a family history of connective tissue disorders or cardiac-related diseases. In addition, the patient reported not having a history of insect bites, nausea, vomiting, diarrhea, alcohol use, or illicit drug use.

Upon checking his vital signs, he was hypoxemic despite being administered 15 L non-rebreather mask with oxygen saturation of 70% for 15 min and an increased respiratory rate (30 breaths per minute). His other vital signs were generally stable, and he was afebrile.

Upon physical examination in the ED, the patient was able to breathe spontaneously but could hardly speak and exhibited an altered sensorium. His peripheral pulse was palpable, cardiac auscultation revealed normal S1 and S2 sounds with no evident murmurs, he had no evident jugular vein distension, chest examination revealed equal bilateral air entry with crackles all over his lung fields, and his extremities were not edematous. Examination of the skin revealed no redness, swelling, needle pricks, bites, or wounds.

During patient workup, electrocardiography (ECG) revealed no signs of ischemia or right ventricular strain (Figure 1). Chest radiography revealed flash pulmonary edema (Figure 2).

Laboratory tests were performed, including venous blood gas analysis (Table 1), which revealed acute respiratory acidosis (PCO2: 73 mmHg, pH: 7.13).

Other laboratory test results were (Table 2): lactate concentration, 3.2 mmol/L, white blood cell count of 20.5×109 cells/L, and normal level of creatinine, hemoglobin, procalcitonin, and bicarbonate. The troponin and brain natriuretic peptide (BNP) concentrations were 164 pg/mL and 125 pmol/L, respectively.

Given that the patient had type 1 and type 2 respiratory failure, intubation was performed, which was successful. Following intubation, he had cardiac arrest, with pulseless ventricular tachycardia, and return of spontaneous circulation (ROSC) was achieved after 1 cycle. After ROSC, the patient became hypotensive. Therefore, a central venous catheter was inserted for vasopressor support, and an axillary arterial line was inserted to accurately monitor blood pressure. Although his condition was better than it was before intubation, he remained hypoxic despite being on maximum mechanical ventilator settings, with a positive end-expiratory pressure greater than 10 cm-H2O, fraction of inspired oxygen of 100%, achieving oxygen saturation of only 85% after 30 min.

Cardiology and intensive care unit teams were involved early and collaborated with the emergency medicine team, leading to the decision to start diuresis. Immediately thereafter, a transthoracic echocardiography (TTE) was arranged with performed, which revealed no abnormalities in the coronary vasculature (Figure 4). Pre-operative transesophageal echocardiography (TEE) confirmed the features of the previous TTE showing ruptured mitral valve chordae with flail anterior leaflet, in addition to partial avulsion of the posteromedial papillary muscle, causing torrential mitral regurgitation, and no signs of endocarditis (Videos 1–3). After hemodynamic stabilization, the patient underwent emergency mitral valve replacement the following day.

During the operation, the patient’s left atrium was opened to expose the mitral valve and the papillary muscles were closely inspected, revealing that both papillary muscles were ruptured, Cardiology, which revealed normal left ventricular function, an ejection fraction >60%, no wall motion abnormalities, and no right ventricular dilation. However, he had acute severe mitral regurgitation accompanied by PMR from the head of the mitral valve to the anterior mitral valve leaflet, and the mitral regurgitant jet was posteriorly directed (Figure 3).

Cardiac Surgery was urgently contacted for assessment and mechanical support, as the patient was in cardiogenic shock. They decided to use an intra-aortic balloon pump (IABP) until the patient stabilized and then could be surgically treated. Cardiology admitted the patient and prior to the insertion of the IABP, emergency coronary angiography (PCI) was resulting in severe incompetence of the mitral valve. No signs of endocarditis were observed. The redundant chordae and tip of the papillary muscle were re-implanted into the mitral annulus.

Other workups that were sent included 2 sets of blood cultures, a C-reactive protein test, an erythrocyte count, and a sedimentation rate test, all of which returned negative. Along with the TEE and surgical observations, the possibility of endocarditis was low. In addition, the initial troponin concentration (164 pg/mL) and serial ECG were unremarkable for ischemic changes, and the serial troponin concentrations decreased, first to 142 pg/mL and then to 100 pg/mL. Moreover, the initial BNP concentration was 125 pmol/L. The patient was weaned off the IABP, ventilator, and vasopressor support uneventfully. After 17 days, he was discharged home with a satisfactory neurological outcome and no complications.

Discussion

We present a unique case of PMR in a middle-aged man without conventional risk factors. This underscores the need to consider acute mitral regurgitation as a potential cause of acute pulmonary edema, despite its rarity. Great emphasis should be placed on the possibility of MI when encountering a patient with acute pulmonary edema, among other causes; however, acute PMR should also be considered as a cause. Although rare, PMR classically occurs after MI, with an incidence in 0.029% in the United States[1]. According to Burton and Beier [4], other “documented etiologies of rupture include trauma, syphilis, periarteritis nodosa, vegetating valvulitis, myocardial abscess, and cocaine use.” Iatrogenic causes have been reported in the literature, following PCI a patient with PMR because of a coronary artery dissection [6]. Patients may also have infective endocarditis with mitral valve rupture or an abscess, or they may have connective tissue diseases. According to the Updated Modified Duke Criteria in 2023, our patient did not meet the new modified Duke criteria for infective endocarditis, as his intraoperative inspection findings were not suggestive for endocarditis [5]. The management of such patients is challenging, as they have a high in-hospital mortality rate [1]. Our patient experienced anterior leaflet PMR, evident via both TTE and TEE, which is supported by the literature, unlike PMR following MI, which would likely result in posteromedial PMR [4]. During surgery, the papillary muscles were closely inspected, revealing that both were ruptured. Another study demonstrated predominance of posterior leaflet PMR in non-ischemic PMR (54.4%) [4]. According to a case report, an elderly patient had spontaneous PMR with a satisfactory outcome after prompt recognition and immediate valve replacement surgery, which was similar to our case [3].

Conclusions

This report describes a case of spontaneous acute PMR of unknown etiology, with few other cases reported in the literature [2–4]. It showcases the abilities and importance of emergency medicine physicians in the best manner where immediate recognition of such rare entity is a required. It also sheds the light on the importance of adopting an early multi-disciplinary team approach, and shows the existence of this rare entity of spontaneous PMR without an identifiable cause.