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Septal ablation in a patient with hypertrophic obstructive cardiomyopathy and a unique variant of anomalous origin of the left coronary artery

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A 71 year old woman was referred for assessment of a severe form of hypertrophic obstructive cardiomyopathy. She complained of chest pain and shortness of breath on exertion. She had an uncertain family history of heart disease, but there was no family history of sudden death. Her history included hypothyroidism, hypertension, and cerebrovascular accidents with minimal sequelae. She had moderate stenosis of the right internal carotid artery. The patient was taking verapamil (240 mg/day) and atenolol (50 mg/day).

Physical examination revealed a 3/6 systolic ejection murmur radiating towards the neck; there was no ejection click. Blood pressure was 180/100 mm Hg and she was in sinus rhythm (heart rate 57 beats/min).

Electrocardiography showed left ventricular hypertrophy with giant T wave inversion and ST segment depression in the anterior and lateral leads. Chest radiography showed an increased cardiothoracic ratio of 16:27. Cross sectional echocardiography showed a 3.8 mm thick intraventricular septum. The left ventricular outflow tract gradient was 65 mm Hg at rest and increased to 120 mm Hg with dobutamine infusion. There was mild to moderate mitral incompetence.

The patient underwent left and right heart catheterisation, and a transeptal approach was used for left ventricular pressure monitoring. Mean outflow tract gradient at rest was 35 mm Hg, which increased to 150 mm Hg after 2 mg of dobutamine (fig 1A).

Figure 1

Simultaneous left ventricular and aortic pressure tracings at rest and after provocation with intravenous isoprenaline. The resting left ventricular outflow tract pressure gradient is completely abolished after the procedure, the very high pressure gradient after isoprenaline provocation is largely reduced following the procedure.

Coronary arteriography showed a relatively small left coronary artery giving branches directed vertically into the intraventricular septum (fig 2A). Selective right coronary arteriography showed a dominant right coronary artery with the circumflex arising from the proximal part of the right and running posteriorly between the aorta and the pulmonary artery. The left anterior descending coronary artery originated from what appeared to be a large conal branch, putting this anomaly into the extremely rare group of single coronary artery of the right “malignant” type. The persistence of the solitary left septal perforator makes this a unique finding. All three major branches were free from degenerative changes.

Figure 2

Angiographic documentation of the “left” coronary artery (A) showing a number of septal perforators originating from one common artery, which has its origin in the left sinus of Valsalva. (B) Presence of an over the wire balloon catheter in the principal artery. The balloon obstructs the lumen completely. The angioplasty guidewire is seen in the largest septal perforator. The transeptal Brochenbrough catheter and the pacemaker electrode in the right ventricle are seen in the left lower corner.

Alcohol ablation1 of the first small septal branch of the isolated left coronary perforator was carried out but with no significant effect on the resting gradient. A balloon was then inflated in the main trunk of the “left” coronary artery about 2 cm away from the ostium (fig 2B). During temporary occlusion of this branch, the systolic gradient disappeared and even isoprenaline provocation failed to provoke any significant pressure gradient. It was therefore decided to ablate the entire “left” coronary artery, which appeared to be responsible for most of the upper septal perfusion. This was done by an injection of 5 ml of absolute alcohol during which the patient complained of serious chest pain. There were more than 3 mm anterolateral and inferior ST segment depression and some extrasystoles often in couplets. At the end of the procedure the resting gradient was abolished and the peak gradient during isoprenaline stress was 45 mm Hg (fig 1B).

There was a moderate rise in creatine kinase (CK) (2220 U/l; CK-MB 269 U/l) and ECG changes reverted to normal in a few hours. Cross sectional echocardiography performed 24 hours later showed a resting gradient of 35 mm Hg and a reduction of the septal thickness to 2.7 mm Hg. Mitral valve incompetence was unchanged. The patient reported profound clinical improvement at six weeks’ and seven months’ follow up.

Therapeutic occlusion of this, probably unique, separately originating septal system resulted in dramatic haemodynamic improvement. The risk of suppressing this vessel seemed minimal in view of the excellent state of the right coronary artery that supplied the rest of the myocardium.