Introduction
A four-leafed (quadricuspid) aortic valve is a rare congenital heart defect with an incidence of less than 0.05 to 1%. The first described case dates back to 1862, and, according to the literature, more than 200 cases have been described since then. The advancement of diagnostic devices has greatly facilitated diagnosis, although most newly diagnosed cases are still registered during cardiac surgery. Despite numerous hypotheses, embryogenetic development has remained incompletely elucidated. Possible mechanisms of development include abnormal proliferation of the common trunk mesenchyme and abnormal fusion of the aorticopulmonary septum with the ultimately developed aberrant endocardial pad. Although it is a congenital anomaly, it is recognized late, only in the fifth or sixth decade of life, given the long-preserved functional status of the heart. Due to the wide range of possible complications, it can manifest even earlier. (1,2)
Case report
In February 2021, we hospitalized a 68-year-old patient due to recurrence of paroxysmal atrial fibrillation at the Department of Cardiology. The patient was tachycardic upon admission, but hemodynamically stable and without respiratory distress, with no signs of volume overload. The patient had a history of long-term arterial hypertension (more than 20 years according to available medical documentation), optimally regulated with antihypertensive therapy and with suboptimal regulated dyslipidemia. In outpatient cardiac controls, LDL cholesterol levels above 4 mmol/L had been monitored for the last 20 years with a note that the patient discontinued statin therapy. Since 2008, he has been in urologic care for prostate adenoma and bilateral nephrolithiasis, and lithotripsy of bladder concrements was performed in 2019. The patient had no other cardiovascular risk factors. He was first hospitalized at the Department of Cardiology ten years earlier, also for paroxysmal atrial fibrillation. At the time, sinus rhythm was achieved by pharmacological conversion with propafenone. After discharge, very rare paroxysms of atrial fibrillation were observed despite the fact that the patient was not taking the recommended antiarrhythmic or anticoagulant therapy. Transthoracic echocardiography (TTE) registered a suboptimal view of the aortic valve with suspected prolapse of the right and noncoronary cusp, and Doppler showed a mild degree of aortic regurgitation. The aortic root measured 40 mm. Global left ventricular systolic function was preserved.
At the last admission to the cardiology department in 2021, sinus rhythm was achieved by pharmacological cardioversion with amiodarone. Cardioversion was preceded by a TTE exam with findings similar to earlier ones. The left ventricle was of borderline size (LVIDd 5.5 cm) with concentrically hypertrophic walls (1.4 cm), well-preserved segmental contractility and with preserved systolic function (LVEF about 70% according to 2D calculation). The left atrium was mildly dilated, and a central aortic regurgitation jet was described (AR 2-3 +) with a stationary dilated aortic root. Examination by transesophageal echocardiography (TEE) ruled out the presence of a thrombus in the left atrial auricle, and multiple projections revealed an aortic valve with four almost identical leaflets of relatively well preserved coaptation and morphologically mild thickening at the tips (Figure 1, Figure 2, andFigure 3). A central jet of aortic regurgitation of moderate degree was observed from the long axis (Figure 4). Given the size and distribution of the cusps, we characterized the quadricuspid aortic valve as type A according to the Hurwitz and Roberts classification. Normal coronary artery orifices were also observed. The patient was soon discharged in good general condition and with a normal sinus rhythm. In further follow-up, he was subjectively without problems, had no chest pain and tolerated physical exertion well. Echocardiographic parameters of aortic regurgitation and aortic root dimensions remained unchanged. Taking into account the morphological and functional state of the aortic valve, the degree of insufficiency and dilated aortic root, further supervision is indicated for now.
Discussion
While Hurwitz and Roberts rank quadricuspid valve defects into 7 types (A-G) according to the size and location of the cusp, Nakamura et al. categorized them more simply into 4 types (I-IV), also depending on the size and distribution of each cusp. (1,3) The first two types in both classifications are equal (types I and II correspond to types A and B), and Tsang et al. have demonstrated that types A (64%) and B (32%) are the most common. The predominant defect of such anatomically developed valves is aortic regurgitation, which progresses to severe regurgitation in one-fifth of patients, which is when cardiac surgery or replacement is required. (4) In a retrospective study conducted in 2004, Tutarel recorded 186 patients with quadricuspid aortic valve, of whom 74% had aortic regurgitation, 0.7% had stenosis, and 8.4% had combined aortic valve regurgitation (regurgitation with stenosis). (5) However, Tsang et al. noted 8% of cases of stenosis in a total of 50 patients with quadricuspid aortic valve. The main culprit for deterioration of the functional status of such an anatomically structured valve is considered to be progressive cusp fibrosis with consequent impaired coaptation. Poorly developed cusp wall, myxoid degeneration, and cusp calcification may also play a role complementary to fibrosis.
It is not known to what extent quadricuspid aortic valves are more susceptible to infectious events than tricuspid or bicuspid valves. There have been several reported cases of infective quadricuspid aortic valve endocarditis. While some authors suggest mandatory antibiotic prophylaxis, most believe that antibiotic prophylaxis should be administered in cases where the size of the cusps is uneven and there is a clearly proven active infection. (1,4)
It is important to note that quadricuspid aortic valves are often an isolated congenital heart defect, although the coexistence of other cardiac anomalies is possible (in 18-32% of cases). Tsang et al. echocardiographically demonstrated concomitant dilated aortic root in 29% of patients, but most had mild dilatation. In a study conducted at the Cleveland Clinic, out a total of 19,722 patients who underwent aortic valve surgery between 1989 and 2010, 31 (0.0016%) had a quadricuspid valve observed during surgery. In 13 of 31 patients (42%) dilatation of the ascending aorta to >4 cm was registered, and an abnormal origin of coronary orifices was found in 10% of patients (3/31). (6) A review of the literature found rare cases of concomitant atrial and ventricular septal defects, persistent ductus arteriosus, congenital pulmonary valve stenosis, as well as hypertrophic cardiomyopathy. (7)
Complete replacement of the aortic valve was most often performed during previous cardiac surgeries. The choice of cardiosurgical treatment was mostly chosen intraoperatively, primarily due to the detection of an anomaly only during the surgery itself. The decision was made based on the severity of the valve disease, according to the condition of the cusp and the personal choice of the surgeon. Aortic valve replacement was predominantly preferred in cases of severely deteriorated quadricuspid aortic valve. In 23% of patients, valve repair was performed in the form of resection, which resulted in “tricuspidalization”. In others, a commissure connection was made to obtain a bicuspid aortic valve, and a Ross procedure was reported in one patient (replacement of a defective aortic valve with a pulmonary one). (8) Approximately one-fifth of patients also had concomitant reparation of the ascending aorta. No perioperative mortality has been reported, but complications such as immediate intracerebral ischemic attack have been reported. Previous postoperative follow-ups have been of varying duration, ranging from three to ten years, during which rare cases of moderate stenosis, endocarditis bioprosthesis, and deterioration of the repaired valve requiring replacement have been recorded. (4,6,8)
Conclusion
Although quadricuspid aortic valve belongs to the group of extremely rare congenital heart defects, the incidence is slightly increasing, primarily due to better diagnostic tools. However, most patients discover its incompetence only in middle to late life, and about a fifth of them will require surgery either in terms of reparation or complete valve replacement. A small group will be subjected to simultaneous repair of the ascending aorta. Due to suboptimal imaging by TTE, we had only partial insight into the morphological and functional state of the aortic valve and cardiac structures. The newly established diagnosis using TEE puts in focus more active monitoring of the diseased valve and its hemodynamic performance. In conclusion, patients with a quadricuspid aortic valve should be subjected to continuous cardiac supervision for timely application of further treatment. Primarily, continuous supervision refers to echocardiographic monitoring of possible progression of aortic regurgitation, monitoring of aortic dimensions, and assessment of their repercussions on cardiac hemodynamics.