A 32-year old married woman, a domestic servant by profession, came to a general hospital with sudden weakness of the right hand and inability to walk, since the last 10 hours. There was no history of recent febrile illness, trauma to the head or purulent discharge from the ear. However, she always felt tired and short of breath and she had curtailed her working hours for the past 1 year. She also experienced episodic palpitations and dizzy spells, ever since the birth of her second child, 3 years back. She recollected being extremely breathless in the last trimester of her pregnancy and her obstetrician strictly advising her not to bear any more children. The patient also distinctly remembered having been incapacitated by severe joint pains for over a month, when she was 15 years of age. On examination, she was anxious and tachypneic. Her tongue and palms were pale but there was no cyanosis or icterus. The pulse was irregular, low in volume at a rate of about 90 beats/min. while the heart rate was around 110 beats/min. The BP was 104/72 mm Hg in the right arm and all peripheral pulses were palpable. The JVP was raised and there was mild pitting edema over the ankles. The apex beat was normal in character and a left parasternal heave was felt. The S1 was variable in intensity and the P2 was loudly audible. A low-pitched mid-diastolic rumble was heard over the cardiac apex, which did not accentuate in pre-systole. The lung fields were clear on auscultation. On neurological examination, power in the right hand and at the elbow was grade 3 while power in the right knee was grade 4. Sensations were preserved and the deep tendon reflexes were diminished on the right side. The was also a right supranuclear facial nerve palsy and slight slurring of speech.
From the history and physical examination, this woman had rheumatic heart disease with mitral stenosis and atrial fibrillation. In all likelihood, she had an embolic stroke due to a dislodged fragment of a left atrial thrombus, which occluded the left middle cerebral artery and caused hemiparesis. An irregular pulse, with a pulse rate deficit compared to the heart rate, are signs of atrial fibrillation. The S1 is variable in intensity, because of a beat-to-beat variation of the diastolic filling period. In the presence of atrial fibrillation, the middiastolic murmur does not undergo presystolic accentuation, because the atrial contribution to ventricular filling is absent.
As expected, the ECG showed atrial fibrillation with a fast ventricular response . Additionally, there was evidence of right ventricular hypertrophy and right-ward deviation of the QRS vector. X-ray chest findings were cardiomegaly, straightening of the left heart border with a prominent atrial appendage as well as signs of interstitial pulmonary edema. On ECHO, the left ventricle was normal but the left atrium and right ventricle were dilated. The mitral valve leaflets were thickened and showed limited excursion with diastolic doming . The aortic valve was structurally normal. No mass or thrombus was demonstrated in any cardiac chamber. The pulmonary artery pressure, as estimated from the tricuspid regurgitant jet, was elevated.
Enlargement of the left atrial appendage is typical of mitral valve disease, be it stenosis or regurgitation, especially when due to rheumatic heart disease. Probably acute rheumatic carditis damages the left atrial wall and its appendage, causing them to bulge when the atrial filling pressure rises. Enlargement of the left atrial appendage causes straightening of the left heart border on chest X-ray . The “4-bump heart” is formed above downward by the aortic knuckle, pulmonary artery, left atrial appendage and the left ventricular lateral wall. The risk of thromboembolism in mitral stenosis is very high, particularly if atrial fibrillation is present and more so if it is intermittent. Mitral stenosis can be safely assumed to be the cause of cerebral infarction, even if a left atrial thrombus is not demonstrable. A thrombus that is too small for detection, thrombus in the atrial appendage or one that has already embolised, may be missed on
transthoracic echo. Transesophageal echocardiography (TEE) vastly improves the detection of a thrombus in the left atrial cavity or its appendage. Occasionally, an ECHO may show a very large atrial thrombus, which is potentially fatal if it suddenly obstructs the mitral valve. Such a ‘ball-valve’ thrombus is an indication for urgent surgical intervention. A left atrial thrombus sometimes needs to be differentiated from a left atrial myxoma, since both can cause distal embolism. Thrombus usually arises from the posterior atrial wall or floats freely, while myxoma is usually pedunculated and is attached to the inter-atrial septum. Thrombus is rounded in shape and uniform in echogenicity, while myxoma is often lobulated with variable echogenicity due to areas of hemorrhage, necrosis or calcification. Finally, thrombus uncommonly prolapses into the diseased mitral valve while myxoma commonly prolapses into the normal mitral valve. The differences between atrial thrombus and atrial myxoma are given in . Besides an atrial thrombus and an atrial myxoma, other structures that may be sometimes seen in the left atrium are supravalvular ring (cor triatriatum), dilated coronary sinus, anomalous pulmonary veins, large mitral leaflet vegetation and reverberation artefacts from a calcified mitral annulus.
In a patient of mitral stenosis and atrial fibrillation with a thrombo-embolic stroke, the first priority is anticoagulation. Low molecular-weight heparin(LMWH) such as enoxaparin is preferred because of predictable pharmacokinetics, without the need of prothrombin time (PT) and aPTT monitoring. An oral anticoagulant like warfarin is initiated almost simultaneously, since it requires 3 to 5 days to produce optimal anticoagulation. Oral anticoagulation is required on a long-term basis in a patient of mitral stenosis with history of thromboembolism. Other cardiovascular drugs are used to reduce the symptomatology of mitral stenosis. Diuretics reduce pulmonary congestion, especially in those with concomitant mitral regurgitation. Digoxin, beta-blockers and verapamil control the ventricular response in atrial fibrillation and improve left ventricular diastolic filling. Percutanenous balloon mitral valvuloplasty (BMV) in not advocated in patients with a demonstrable left atrial thrombus. Mitral valve replacement is required for critical stenosis (mitral valve area < 1 cm2).