Dynamic left ventricular outflow tract obstruction due to anemia in a 71-year-old patient with sigmoid septum

Summary

Sigmoid septum, although frequently observed in the elderly, has no pathophysiological significance in general. A 71-year-old woman with sigmoid septum developed acute heart failure because of a significant left ventricular outflow tract obstruction associated with the aggravation of anemia. This report provides the evidence that a hypercontractile cardiac state induced by anemia can be critical, especially in patients with sigmoid septum. Assessment of the left ventricular outflow tract pressure gradient is important in heart failure patients with sigmoid septum and dynamic obstruction.

Introduction

Left ventricular outflow tract (LVOT) obstruction is typically observed in patients with hypertrophic cardiomyopathy, i.e. hypertrophic obstructive cardiomyopathy [1]. Dynamic LVOT obstruction is also observed during catecholamine excess [2], exercise overload, anorexia [3], dehydration, concentric hypertensive hypertrophy [4], after aortic- or mitral valve repair, and Takotsubo cardiomyopathy [5]. Although rare, patients with sigmoid septum also exhibit dynamic LVOT obstruction during exercise overload, lumber anesthesia [6], or surgery. We present a case of anemia-induced dynamic LVOT obstruction in an elderly patient with sigmoid septum.

Case report

A 71-year-old woman with no history of cardiovascular events was hospitalized for dyspnea on effort. On admission, her blood pressure was 200/100 mmHg, and a chest radiograph showed moderate-to-severe pulmonary congestion. Laboratory data revealed moderate macrocytic anemia: her blood hemoglobin (Hb) concentration was 7.4 g/dL and hematocrit value was 26%. Cardiac catheterization revealed a normal coronary angiogram and 80 mmHg pressure gradient at the LVOT. On the basis of these findings, the patient was diagnosed with acute decompensated heart failure due to elevated blood pressure and LVOT obstruction. In addition to treatment with diltiazem (100 mg/day) and carvedilol (5 mg/day), oral cibenzoline (100 mg/day) was administered to diminish the pressure gradient and alleviate the symptoms [7]. The patient was eventually discharged from the hospital, and subsequently underwent an esophagogastric endoscopy, which revealed a gastric ulcer. This ulcer was considered to have caused anemia and was treated with a proton pump inhibitor. Nevertheless, her symptoms were aggravated again when her Hb concentration dropped below 8 g/dL. She had to be rehospitalized because an increase in the dose of cibenzoline to 200 mg/day was not sufficient to alleviate her symptoms. Physical examinations on admission were as follows: blood pressure, 103/49 mmHg; bisferious pulse over the carotid artery; pale conjunctivae; and grade-3 systolic ejection murmur. An electrocardiogram showed sinus rhythm at a rate of 62 bpm. A chest radiograph showed mild pulmonary congestion without cardiomegaly. Her blood Hb concentration was 4.5 g/dL and her hematocrit value was 14.6%. Two-dimensional transthoracic echocardiography revealed a marked bulging of the sigmoid septum (Fig. 1A). The left ventricular wall thickness was normal (the ventricular septum was 1.1 cm and the posterior wall was 0.9 cm) with no segmental hypertrophy, and wall motion was hyperkinetic (54% fractional shortening). The mitral valve showed systolic anterior motion and septal contact of the anterior leaflet (Fig. 1B), which was accompanied with moderate-to-severe mitral regurgitation. The peak systolic flow velocity across the LVOT was 6.3 m/s, which was equivalent to a pressure gradient of 156 mmHg (Fig. 1C). The patient was transfused with 800 mL concentrated red cells, which restored her Hb concentration to 12.4 g/dL and significantly decreased the LVOT pressure gradient to 14 mmHg (Fig. 2A). Subsequently, echocardiography revealed no septal contact of the mitral valve, except for a mild anterior motion of the anterior leaflet (Fig. 2B). Residual regurgitation of the mitral valve was not significant. The patient's symptoms subsided, and she was discharged from the hospital.

Figure 1.

(A) Two-dimensional transthoracic echocardiography performed on admission. A parasternal long-axis view showed the basal interventricular septum bulging into the left ventricular outflow tract (LVOT). (B) M-mode echocardiograph showed systolic anterior motion and septal contact of the anterior mitral leaflet. (C) Continuous wave Doppler echocardiography across the LVOT revealed a peak flow velocity of 6.25 m/s equivalent to a pressure gradient of 156 mmHg.

Figure 2.

(A) Doppler flow velocity measurement and M-mode echocardiography after transfusion revealed a peak flow velocity of 1.89 m/s equivalent to a pressure gradient of 14.3 mmHg across the left ventricular outflow tract. (B) M-mode echocardiography after transfusion revealed mild anterior motion but no septal contact of the anterior mitral leaflet.

Discussion

Sigmoid septum is an angulation between the basal interventricular septum and the ascending aorta. Although sigmoid septum by itself has no pathological or clinical significance [8], a hypercontractile cardiac state and decrease in the intravascular blood volume may narrow the LVOT and result in dynamic obstruction in clinical settings such as catecholamine excess [2], exercise overload, sympathetic activation, and dehydration. It has also been reported that nifedipine can aggravate LVOT pressure gradient as a result of vasodilation of the peripheral circulation [9]. Weiskopf et al. have reported that moderate-to-severe anemia decreases the systemic vascular resistance and increases stroke volume, heart rate, and cardiac index [10]. Sympathetic activation has also been reported in patients with anemia [11]. Recently, Kubo et al. have reported a patient with hypertrophic obstructive cardiomyopathy accompanied with hemolytic anemia [12]. Although the patient had no evidence of hypertrophic cardiomyopathy, anemia-induced hyperdynamic circulation may have resulted in the recurrence of acute heart failure due to the LVOT obstruction with sigmoid septum. Moreover, gastrointestinal bleeding from the gastric ulcer could have decreased the blood volume and may have been crucial for the development of LVOT obstruction. In accordance with a previous report [7], treatment with cibenzoline was initially effective against the LVOT obstruction; however, it was not sufficient to alleviate the symptoms associated with the progression of anemia during the second hospitalization. Optimal control of hemodynamics, oxygen supply, and intravascular blood volume, therefore, should be focuses of medical intervention in patients with dynamic LVOT obstruction. On the other hand, moderate-to-severe mitral regurgitation might play a role for the development of acute decompensated heart failure. Since the mitral regurgitation disappeared concomitantly with the improvement of LVOT obstruction, it was probably as a result of the LVOT obstruction, which caused systolic anterior motion of the anterior leaflet and an increase in the left ventricular pressure. This case clearly demonstrates that anemia-induced hemodynamic disturbance may cause dynamic LVOT obstruction, resulting in the development of acute heart failure in patients with sigmoid septum.