A Case of Left Main Systolic Compression Caused by a Dilated Pulmonary Artery in a Patient with Congenital Pulmonic Stenosis

ABSTRACT: Dynamic compression of the left main coronary artery during systole is extremely rare. We report a case of a 29-year old female who presented with shortness of breath and chest pain with exertion. She had a history of congenital pulmonic stenosis and had a pulmonary valve resection at age 2. She subsequently developed chronic pulmonic insufficiency. She had normal left ventricular systolic function and a dilated right ventricle with pressure and volume overload diagnosed by echocardiography. She had pulmonary artery hypertension with pulmonary artery pressures noted to be systolic of 62mmHg, diastolic of 10 mmHg, mean of 29 mmHg on right heart catheterization. Her echocardiogram also showed an elevated mean pulmonary artery pressure of 25 mmHg, which was thought to be due to increased flow. On left heart catheterization, she was found to have dynamic systolic compression of the left main coronary artery by a dilated pulmonary artery. This is the first case report of a patient with congenital pulmonic stenosis with a dilated pulmonary trunk causing systolic compression of the left main coronary artery. Dynamic systolic compression of the left main coronary artery is a rare cause of angina, is rarely reported, and requires a high level of suspicion and careful investigation for accurate diagnosis. J INVASIVE CARDIOL 2010;22:E176–E179 ————————————————————

Dynamic systolic compression of the left main coronary artery (LMCA) is extremely rare. Pulmonary hypertension and an enlarged pulmonary artery trunk are known causes of fixed systolic compression of the LMCA. This is the first case report of a patient with repaired pulmonic stenosis who was found to have dynamic systolic compression of the left main coronary artery from a dilated and pulsatile pulmonary artery from pulmonary hypertension and severe pulmonary insufficiency.

Case Report. A twenty-nine year old female presented to our medical center for evaluation of right-sided heart failure, pulmonary hypertension and a history of congenital pulmonic stenosis. She underwent a pulmonary valvectomy at age 2 for congenital pulmonic stenosis and was clinically asymptomatic until her first pregnancy. She became pregnant at the age of 22 and did have significant dyspnea towards the end of her pregnancy, requiring bed rest. She now presented to a local emergency room with complaints of chest pain. An echocardiogram showed evidence of right heart failure and elevated pulmonary artery pressures. She was referred to our center for evaluation of right heart failure and severe pulmonary insufficiency.

The patient had a 2 pack-year history of tobacco use. She occasionally smoked marijuana and rarely drank alcohol. She had a history of using over-the-counter anorexigens, but no prescription anorexigens. Family history was noncontributory. She had no allergies and was on no medications. On physical exam, her pulse was 78 and blood pressure was 120/86. She had elevated jugular venous pressure. She had a 3/6 systolic murmur at the left sternal border and a 3/6 diastolic murmur consistent with pulmonic insufficiency.

The patient underwent right and left heart catheterization for evaluation of right-sided pressures and for coronary evaluation prior to a planned pulmonic valve prosthesis placement. On right heart catheterization, her pulmonary artery systolic pressure was 62 mmHg, pulmonary artery diastolic pressure was 10 mmHg, with a mean of 29 mmHg. A wedge pressure was unable to be obtained due to inability to wedge the Swan Ganz catheter. There was no evidence of shunts by oxygen saturations. Coronary angiography showed dynamic systolic compression of the proximal portion of the LMCA resulting in a 60–70% stenosis. During diastole, there was no significant compression. 64-slice computed tomography scan (CT) was obtained to evaluate the cause of systolic compression of the left main that was thought to be from extrinsic compression by a dilated pulmonary artery. The CT showed evidence of systolic phase enlargement of the main pulmonary artery with caudal displacement of the inferior wall of the main pulmonary artery. The degree of narrowing could not be determined due to the degraded image quality in systole on the cardiac CT. Her ascending aorta measured 2.5 cm in diameter in diastole and the main pulmonary artery measured 4.0 cm in diameter in diastole.

Surgical intervention with replacement of the pulmonic valve was advised. The patient underwent pulmonic valve replacement without complications with a bioprosthetic #23 Magna valve. She had an uneventful post-operative course.

Discussion. Extrinsic compression of the LMCA was first described in 1957 by Corday et al in a patient with pulmonary hypertension.¹ Since then, extrinsic LMCA compression by a dilated pulmonary artery has been well described in patients with pulmonary hypertension.^3,4 However, prior reports have described fixed compression throughout the cardiac cycle. Dynamic systolic compression of LMCA, however, is extremely rare. The known risk factors for LMCA compression are acyanotic congenital heart disease, especially atrial and ventricular septal defects, Eisenmenger type ductus arteriosus, and pulmonary hypertension.² The incidence of LMCA narrowing in patients with an atrial septal defect and pulmonary hypertension ranges from 44% in one report to 4.8% in a study by Kothary et al.^3,4 All these cases described fixed extrinsic compression. Dynamic compression of the LMCA is extremely rare and to our knowledge, only two case reports have been published. One case was in a patient with severe pulmonary hypertension and dynamic compression was confirmed by IVUS but was not prominent enough to be seen angiographically.¹⁶ The other case was of severe left atrial enlargement secondary to mitral regurgitation causing dynamic compression of the left main coronary artery.¹⁸ Dynamic compression of other coronary arteries is quite common and well described especially from myocardial bridging.^7,19,20,21 However, the LMCA does not usually have an intramyocardial course and thus this has not been reported as a etiology of systolic compression of the LMCA.

Approximately one-third of patients with pulmonary hypertension experience angina during the course of the disease. Four causes of angina in patients with pulmonary hypertension were suggested by McGoon and Cane: 1) progressive right ventricular stress causing increased myocardial oxygen demand; 2) critically elevated right ventricular systolic pressure reducing the pressure gradient from the epicardial right coronary artery to the subendocardium, thus reducing coronary flow; 3) development of concomitant atherosclerotic coronary artery disease; or 4) compression of the left main coronary artery by the dilated main pulmonary artery.^6–8

Risk factors for LMCA compression in patients with pulmonary hypertension include a leftward origin of the left coronary artery origin, a dilated pulmonary trunk, and an elevated pulmonary trunk to aortic diameter ratio. In a case series of 12 patients, a LMCA takeoff angle was also suggested to play a part in the degree of obstruction imposed by the pulmonary artery. Kajita et al suggested that a leftward origin of the LMCA in the left sinus of Valsalva may be protective against compression by the pulmonary trunk. A left coronary takeoff angle (measured in the left anterior oblique projection with cranial angulation) of less than 45 degrees correlated to the patients with left main compression as compared to patients without left main compression. Taylor et al showed that a LMCA origin angle was frequently found in patients with sudden death and isolated coronary anomalies.⁵ Mesquita et al suggested that pulmonary trunk diameter is helpful in selecting patients at risk for systolic compression of the left main. In their study, 37% of patients with a pulmonary artery diameter of > 40 mm had evidence of left coronary compression. Similarly, patients who had a pulmonary trunk to aortic diameter ratio of greater than 1.21 had a rate of coronary artery compression of 26%, whereas those patients with a ratio less than 1.2 had no evidence of coronary artery compression.¹⁵

Myocardial bridging is one of the most common causes of coronary artery systolic compression. Patients with myocardial bridging typically follow a benign course; however, there have been a few case reports suggesting complications as acute myocardial infarction, ventricular tachycardia, syncope, atrioventricular block and sudden cardiac death.^6,19,20 The most common clinical presentation in patients with myocardial bridging is stable angina, followed by atypical angina, dyspnea and syncope.¹⁹ Myocardial bridging is not seen in LMCA, as the vessel does not course through the myocardium.

Diagnosing systolic compression of the coronary artery as the cause of a patient’s anginal symptoms can be difficult. Intravascular ultrasound (IVUS) and nuclear stress testing have helped in diagnosis of anginal symptoms caused by compression of the left main.^9,7 IVUS has also helped diagnose angiographically unapparent myocardial bridging.^21,22 Current recommendations include assessing systolic compression with angiography, IVUS, fractional flow assessment and nuclear stress testing.^16,22 Coronary CTA can be beneficial; however, many CT coronary angiography protocols are optimized for viewing the coronaries during diastole. For visualization of systolic compression, many protocols may need to be changed. That being said, 64-slice cardiac CT provides a good method for evaluating the degree of LMCA compression, the angulation of the LMCA relative to the left sinus of Valsalva, the evaluation of left and right ventricular function, and pulmonary pathology.²³

Treatment of LMCA compression by the pulmonary artery is dependent on the cause and reversibility of the pulmonary trunk dilatation. Percutaneous stent placement in the LMCA has been successful in many case reports.^6,7,23 Lung transplantation, coronary bypass grafting, pulmonary trunk plasty and atrial septal defect closure (to reduce right heart volume overload causing pulmonary root dilatation) have also been performed successfully.^9–12,14 The results from stenting tunneled intramyocardial coronary arteries is poor and not routinely recommended without evidence of significant inducible ischemia or atherosclerosis.²² In our patient, correction to the cause of a dilated pulmonary trunk assisted with symptom relief. Unfortunately, we do not have a follow-up catheterization or cardiac CT in this patient to confirm the reduction in systolic compression after surgical correction of her severe pulmonic insufficiency.

In summary, dynamic systolic compression of the LMCA is rare and may cause anginal symptoms. Our patient with congenital pulmonic stenosis with pulmonic valvulotomy at a young age is the first case of severe pulmonary insufficiency causing dynamic compression of the LMCA. Myocardial bridging does not occur in the LMCA, so systolic compression in this artery is exceedingly rare. Left heart catheterization with or without IVUS establishes the diagnosis. Coronary CT or Cardiac MRI can assist with this diagnosis. Therapy and intervention depend on the reversibility of the pulmonary hypertension or obstruction. In our patient, pulmonary valve replacement helped her symptoms.

References

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From the University of Kansas Medical Center, Kansas City, Missouri. The authors report no conflicts of interest regarding the content herein. Manuscript submitted February 4, 2010, provisional acceptance given February 22, 2010, final version accepted March 2, 2010. Address for correspondence: Kamal Gupta, MD, University of Kansas Medical Center, VA Medical Center, Department of Medical Subspecialties, 4801 Linwood Blvd., Kansas City, MO 64128. E-mail: kamal.gupta@sbcglobal.net