Stress testing in patients with hypertrophic cardiomyopathy

Exercise echocardiography is an important and useful tool for the evaluation of symptoms and monitoring the response to therapy in patients with hypertrophic cardiomyopathy (HCM). A significant number of patients without resting left ventricular outflow tract gradients develop dynamic obstruction with exercise. Detection of an exercise-induced gradient provides a therapeutic target for the relief of symptoms. Abnormal blood pressure response to exercise is an important, although nonspecific, risk factor for cardiovascular death in patients with HCM. Stress testing such as myocardial perfusion imaging lacks specificity in diagnosing coronary artery disease in patients with HCM but has a good negative predictive value. Exercise stress test in controlled environment seems to be safe in properly selected patients with HCM, and benefits of the diagnostic and prognostic information obtained outweigh the small risks.     

Left Ventricular Outflow Tract Gradient Provoked by Upright Position or Exercise in Treated Patients with Hypertrophic Cardiomyopathy without Obstruction at Rest

Objectives: The aim of the study was to assess inducibility of left ventricular outflow tract (LVOT) gradient by change of position from supine to upright and by treadmill exercise in treated patients with hypertrophic cardiomyopathy (HCM) without obstruction at rest. Methods: We studied 37 treated HCM patients (21 men and 16 women, mean age 44 ± 12 years) with LVOT gradient <30 mmHg at rest in supine position. The patients were then placed in upright position and the gradient was reexamined. The patients who developed LVOT gradient ≥30 mmHg during this maneuver were not exercised, whereas the remaining patients (nonobstructive in orthostatic position) performed moderate-intensity exercise on a treadmill, with continuous monitoring of the LVOT gradient. For comparison with resting measurements, gradients at peak exercise (in upright position) and at recovery (in supine position) were used. The resting minimal distance between the mitral valve and ventricular septum at systole was used to assess the degree of narrowing of LVOT. Results: The orthostatic position provoked LVOT gradient ≥30 mmHg in 8 of 37 patients. At peak exercise, 10 of the remaining 29 patients developed significant LVOT gradient. At recovery in supine position, this significant gradient disappeared in 6 of 10 patients, despite only a short delay in measurement. Of resting echocardiographic parameters, only systolic mitral–septal distance differentiated between the provocable and nonprovocable subgroups. Patients with provocable gradient (either by changing position or by exercise) presented with lower values of this parameter than the nonprovacable subgroup. Conclusions: In nonobstructive HCM patients under treatment, the LVOT gradient was inducible by upright position in 21.6% and by upright moderate exercise in 34.5%. The minimal septal–mitral distance may be useful to identify patients with provocable obstruction.     

Effect of alcohol-induced septal ablation on left atrial volume and ejection fraction assessed by real time three-dimensional transthoracic echocardiography in patients with hypertrophic cardiomyopathy

Alcohol-induced septal ablation (AISA) is an accepted treatment for hypertrophic cardiomyopathy (HCM) patients with left ventricular (LV) outflow obstruction who are unresponsive to medical therapy. As left atrial (LA) enlargement has been correlated with increased morbidity and mortality in HCM, we assessed LA volumes and ejection fraction (EF) prior to and after AISA using real time three-dimensional (3D) transthoracic echocardiography (TTE) in 12 patients (9 women; mean age 52 ± 15 years; 11 Caucasian). All patients underwent successful AISA with no complications and their resting left ventricular outflow gradients decreased from 40.5 ± 22.2 to 9.1 ± 17.6 mmHg (P < 0.001) while their gradients with provocation decreased from 126.2 ± 31.7 to 21.8 ± 28.0 mmHg (P < 0.001). All patients showed improvements in their New York Heart Association (NYHA) functional class. Both the LA end-systolic (45.2 ± 12.9 to 37.2 ± 13.7 ml, P < 0.0001) and end-diastolic (79.6 ± 18.9 to 77.1 ± 18.6 ml, P = 0.001) volumes decreased after AISA. The LA EF increased from 43.1 ± 9.0 to 52.5 ± 8.8% (P = 0.001). The increase in LA EF correlated with the decrease in the resting left ventricular outflow gradient (R =−0.647, P = 0.03). In conclusion, 3D echocardiography can be utilized to follow LA function after AISA for HCM. AISA results in clinical improvement in patients with HCM and in improvement of LA EF that is correlated with the decrease in the left ventricular outflow gradient.     

Prevalence and significance of left ventricular outflow gradient during dobutamine echocardiography.

AIMS: This study investigated the clinical and physiological significance of the dynamic left ventricle outflow gradient observed in some patients during dobutamine stress echocardiography. METHODS: Three hundred and ninety-four consecutive patients completed dobutamine stress echocardiography using Doppler echocardiography to assess the presence of myocardial ischaemia and left ventricular outflow gradient. The prevalence of left ventricular outflow gradient was evaluated and correlated with echocardiographic and clinical findings. Fifteen patients with left ventricular outflow gradient during dobutamine infusion underwent exercise echocardiography for appearance of left ventricular outflow gradient. RESULTS: Sixty-nine of 394 (17.5%) patients developed a left ventricular outflow gradient of more than 36 mmHg. In nine of them (13%) the anterior mitral valve leaflet had a systolic anterior motion. In 60 of the 69 patients (87%) there was a dynamic obstruction at the level of the papillary muscles. The mean intracavitary gradient was 75.4 (range 36-175) mmHg. There was no correlation between the presence or absence of a dobutamine stress echocardiography-induced left ventricle outflow gradient and chest pain or shortness of breath. In patients who developed a left ventricular outflow gradient ischaemic wall motion abnormalities occurred at a significantly lower frequency during dobutamine stress echocardiography (2.9 vs 16.4% P<0.001). None of the 15 patients who underwent exercise echocardiography developed significant left ventricular outflow gradient. CONCLUSION: Left ventricular outflow gradient occurs occasionally during dobutamine stress echocardiography examination. Its presence is of no physiological or clinical significance.     

Resting and exercise left ventricular function in patients with hypertrophic cardiomyopathy

Left ventricular ejection fraction (EF) at rest and during exercise was measured in 19 patients with hypertrophic cardiomyopathy (HCM) by means of radionuclide angiography. The results were compared to those in 20 normal subjects. Based on hemodynamic data, patients with HCM were divided into three groups. In group I, no demonstrable left ventricular outflow obstruction, there were five patients; their mean EF increased from 68% +/- 8.9 (+/- SD) at rest to 74% +/- 9.2 during exercise (p less than 0.05). In group II, latent obstruction, there were six patients; their mean EF at rest (75.2% +/- 8.2) and at peak exercise (78.7% +/- 6.7) was not statistically different (p greater than 0.05). Group III, obstruction present at rest, consisted of eight patients; EF at rest (82.6% +/- 8.5) decreased significantly during exercise (75.6% +/- 7.7, p less than 0.01). In normal subjects resting EF was 66.3% +/- 7.6; it increased to 76.4% +/- 7 (p less than 0.001). Exercise duration and heart rate-blood pressure product were lower in groups II and III. Thus there are significant differences in left ventricular systolic function both at rest and during exercise between these three major hemodynamic subgroups. These findings emphasize the importance of such a hemodynamic classification of HCM.     

Efficacy of continuous intravenous drip infusion of disopyramide in hypertrophic obstructive cardiomyopathy during cardiogenic shock: a case report

A 54-year-old woman was admitted to our hospital complaining of dyspnea due to hypertrophic obstructive cardiomyopathy. On admission, she was treated with 4 antiarrhythmic drugs and 2 beta-blockers. After 4 of these 6 drugs were withdrawn, the left ventricular outflow pressure gradient markedly increased and then she fell into cardiogenic shock. Therefore, disopyramide(600 mg/day) was administered by continuous intravenous drip infusion to reduce the left ventricular outflow pressure gradient. After intravenous administration of disopyramide, the left ventricular outflow pressure gradient markedly decreased from 100 to 16 mmHg and the cardiogenic shock could be improved. Continuous intravenous drip infusion of disopyramide is effective for the treatment of cardiogenic shock due to severe left ventricular outflow obstruction in patients with hypertrophic obstructive cardiomyopathy.     

Anomalous insertion of papillary muscle directly into anterior mitral leaflet in hypertrophic cardiomyopathy. Significance in producing left ventricular outflow obstruction

BACKGROUND. Obstruction to left ventricular outflow in hypertrophic cardiomyopathy (HCM) is usually due to systolic anterior motion of the mitral valve. Occurrence of structural mitral valve abnormalities in HCM and their significance in producing outflow obstruction (even in the absence of typical systolic anterior motion) has not been fully appreciated. METHODS AND RESULTS. Analysis of 78 mitral valves excised from patients with obstructive HCM showed that 10 (13%) had anomalous insertion of one or both left ventricular papillary muscles directly into the anterior mitral leaflet. This malformation was identified by echocardiography, which demonstrated direct continuity between the hypertrophied papillary muscle and mitral leaflet, resulting in a long rigid area of midcavity narrowing that appeared to be solely or largely responsible for outflow obstruction. Basal subaortic pressure gradients were large (70-150 mm Hg). Mitral valve replacement reduced the outflow gradient substantially to 0-15 mm Hg in four patients with postoperative cardiac catheterization. However, two other patients who underwent septal myotomy/myectomy had persistent symptoms and incomplete relief of obstruction (gradients 60 and 70 mm Hg) because of continued midcavity apposition of papillary muscle and ventricular septum. CONCLUSIONS. Anomalous papillary muscle insertion into anterior mitral leaflet represents a mechanism of obstruction to left ventricular outflow in patients with HCM and differs considerably from typical dynamic obstruction caused by mitral valve systolic anterior motion that occurs in many other patients with HCM. Recognition of this malformation emphasizes the diverse morphological expression of HCM and also has important clinical implications for patients requiring operation because the gradient is likely to persist even after adequate myotomy/myectomy; consequently, mitral valve replacement would appear to be the operation of choice in most such patients.     

Left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy: increase in gradient after exercise.

To define alterations in the magnitude of the left ventricular outflow tract gradient during supine exercise, 10 patients with hypertrophic obstructive cardiomyopathy were studied under basal conditions and during exercise and recovery with simultaneous invasive hemodynamic measurements, particularly of the peak to peak systolic pressure gradient across the left ventricular outflow tract. Basal outflow pressure gradient ranged from 0 to 89 mm Hg (average 37.4 +/- 9.6). No increase was observed during 5 min of exercise (average 29.6 +/- 10 mm Hg, range 0 to 91; p = NS), even though arterial blood pressure, heart rate and cardiac index increased significantly in association with a decrease in peripheral vascular resistance. However, a rapid and highly significant increase in left ventricular outflow gradient occurred after exercise was completed (average 83.5 +/- 11.4 mm Hg, range 10 to 130; p less than 0.001), while arterial blood pressure, heart rate and cardiac index closely approached basal levels and total peripheral vascular resistance increased. In contrast to previous assumptions regarding the behavior of the outflow gradient in hypertrophic cardiomyopathy, obstruction to left ventricular outflow increases after rather than during supine exercise. Rapid changes in preload during recovery represent the most likely explanation for the postexercise development of outflow obstruction. New considerations regarding the mechanisms of sudden cardiac death and the therapeutic approach in patients with hypertrophic cardiomyopathy may result from this pathophysiologic observation.     

Left ventricular systolic dysfunction during exercise and dobutamine stress in patients with hypertrophic cardiomyopathy

OBJECTIVES: We sought to characterize stress-induced left ventricular systolic dysfunction in patients with hypertrophic cardiomyopathy (HCM). BACKGROUND: Myocardial ischemia and diastolic dysfunction occur in patients with HCM. We hypothesized that, in the setting of transient myocardial ischemia, left ventricular systolic dysfunction occurs during exercise and dobutamine stress. METHODS: We studied 39 patients with HCM but without obstructive symptoms at rest or coronary artery disease. A continuous ventricular function monitor equipped with cadmium telluride detectors (VEST) was used to evaluate left ventricular function during supine bicycle ergometer exercise. Dobutamine stress echocardiography (DSE) was also performed. The left ventricular ejection fraction (LVEF) and regional wall motion were determined from echocardiographic images. RESULTS: Changes in the LVEF correlated between exercise and dobutamine stress (r = 0.643, p < 0.0001). The LVEF decreased more than 5% at peak exercise in 17 of patients (group II), while the other patients had normal responses (group I). New regional wall motion abnormalities during dobutamine infusion were detected in 18 of 110 (16.4%) segments in group I and 42 of 85 (49.4%) segments in group II. Decreased or unchanged regional wall motion occurred more frequently in hypertrophied segments than in nonhypertrophied segments (p < 0.0001). There were significant inverse correlations between the LVEF responses during both stresses and the number of abnormal segments noted during dobutamine stress in all patients (VEST: p < 0.005; DSE: p < 0.0005). Signs of left ventricular obstruction were observed in 11 of 39 patients during DSE. However, there was no significant correlation between the LVEF response and the dobutamine-induced left ventricular pressure gradient. CONCLUSIONS: Exercise-induced systolic dysfunction occurred in 50% of patients with HCM. In these patients, regional wall motion abnormalities were present in hypertrophied segments.     

运动负荷超声在评估肥厚型心肌病梗阻类型中的应用

目的 评估肥厚型心肌病(HCM)患者静息和运动中左室流出道梗阻的情况.方法 连续入选的60例静息左室流出道压差(LVOTG) ＜50 mm Hg(1 mm Hg=0.133 kPa)的HCM患者,超声测量静息LVOTG和运动峰值LVOTG.51例静息LVOTG＜ 30 mm Hg的患者中,26例患者运动峰值LVOTG≥30 mm Hg为潜在梗阻,25例运动峰值LVOTG＜ 30 mm Hg为非梗阻.9例静息LVOTG30 ～49 mm Hg为静息梗阻.分析不同类型梗阻的形态学特征.结果 潜在梗阻与非梗阻患者相比,二尖瓣前叶收缩期前向运动(SAM)征(73.1％比8.0％)、流出道狭窄(46.2％比4.0％)更常见、二尖瓣反流程度更重、静息LVOTG[(16.9±7.2) mm Hg比(7.1 ±4.3)mm Hg]更高,室间隔肥厚部位分布差异有统计学意义(P值均＜0.05).多因素logistic回归分析,SAM征(OR 6.431,95％ CI2.323 ～291.112,P=0.002)和室间隔肥厚部位(OR0.011,95％ CI0.001 ～0.179,P=0.008)为发生潜在梗阻的独立预测因素.结论 约半数静息无梗阻的HCM患者存在潜在梗阻.SAM征和室间隔肥厚部位有助于潜在梗阻的识别.     

Effect of exercise on systolic left ventricular outflow velocity in healthy adults

The occurrence of exercise-induced dynamic obstruction of the left ventricular outflow tract in patients without cardiomyopathy has recently been reported. However, it is not known if this phenomenon is a normal response to exercise in healthy adults. We studied 23 healthy adults using exercise Doppler echocardiography. We measured the left ventricular outflow velocity at rest and after maximum tolerated exercise. After a mean exercise duration of 12 min 45 s (2 min 32 s), the heart rate was 97.61 (6.71)% of the theoretical maximum. Left ventricular outflow velocity increased from 1.07 (0.18) m/s (range: 0.77-1.44 m/s) to 1.58 (0.35) m/s (range: 1.09-2.4 m/s). In healthy adults, exercise increased the left ventricular outflow velocity by 50%, though in no subject was it greater than 2.5 m/s. This observation appears to rule out the possibility that a high intraventricular pressure gradient is a normal response to exercise in healthy adults.     

The effect of the atrioventricular interval during atrioventricular sequential pacing on the hemodynamics in dynamic obstruction of the left ventricular outflow tract in dogs

The present study was performed to clarify the mechanism involved in the reduction of the pressure gradient in the left ventricular outflow tract of patients with hypertrophic obstructive cardiomyopathy when treated with atrioventricular (AV) sequential pacing. The effect of AV sequential pacing with variable AV intervals on the hemodynamics and dyssynchronous wall motion was experimentally studied using echocardiography in the dynamic obstruction of the left ventricular outflow tract created by dobutamine infusion in 17 dogs. The pressure gradient of the left ventricular outflow tract decreased with shortening of the AV interval during AV sequential pacing. Also, the dyssynchrony time, defined as the difference in the time between the intraventricular septum and posterior wall during the systolic phase recorded with M-mode echocardiography, increased with shortening of the AV interval during AV sequential pacing. However, very short AV intervals produced a significant decrease in the aortic pressure and increase in the pulmonary capillary wedge pressure. The dyssynchrony time showed a positive liner correlation with the percentage reduction in the pressure gradient of the left ventricular outflow tract (R=0.794, p<0.0001). It was concluded that dyssynchronous wall motion in the left ventricle was produced by pacing from the right ventricular apex and resulted in a reduction in the pressure gradient of the left ventricular outflow tract. Optimization of the AV interval during AV sequential pacing may play an important role in improving the hemodynamics in dynamic obstruction of the left ventricular outflow tract.     

经胸超声心动图评价高血压心脏病与左心室流出道梗阻的应用价值

目的:应用经胸超声心动图(transthoracic echocardiography,TTE),评价高血压心脏病与肥厚型心肌病(HCM)左心室流出道梗阻的二维及血流动力学特征,为临床鉴别诊断提供影像学依据。方法:左心室流出道梗阻患者31例,其中高血压性左心室流出道梗阻12例,肥厚型梗阻性心肌病19例,二维图像下测量两组患者的室间隔厚度及左心室后壁厚度,在静息状态和激发试验后测量两组患者的左心室流出道流速及最大压差,分别进行组间及组内比较。结果:室间隔厚度肥厚型心肌病组(19.6±1.8)mm明显高于高血压组(12.4±0.6)mm,差异有统计学意义(P<0.05)。左心室后壁厚度:肥厚型心肌病组(11.5±0.5)mm,高血压组(11.3±0.6)mm,两组间比较差异无统计学意义(P>0.05)。高血压组组内比较激发试验后左心室流出道流速(398.6±36.7)cm/s及压差[(68.4±12.9)mmHg,1 mmHg=0.133kPa],均高于静息状态下流速178.2±23.4)cm/s,压差(13.5±6.2)mmHg,差异有统计学意义(P<0.05)。结论:经胸超声心动图能准确评价左心室流出道梗阻的解剖结构与血流动力学特征,可准确鉴别梗阻类型及梗阻程度。     

Comparison of ventricular emptying with and without a pressure gradient in patients with hypertrophic cardiomyopathy.

Thirty three patients with hypertrophic cardiomyopathy were studied to determine whether the presence of an intraventricular pressure gradient impaired left ventricular emptying. Patients with resting gradients had a higher mean left ventricular ejection fraction (92 (6.4)%) than patients without a resting or inducible pressure gradient (75.5 (9)%). The rate and degree of emptying increased when gradients greater than 85 mm Hg were induced in two patients with insignificant mitral regurgitation. If the induced gradients had been the result of obstruction a decrease in the rate or degree of ventricular emptying would be expected. Higher ejection fractions in patients with intracavitary pressure gradients as well as enhanced rate and degree of left ventricular emptying with induced gradients are inconsistent with outflow obstruction. These findings support the concept that cavity obliteration is responsible for the pressure gradient in these patients with hypertrophic cardiomyopathy.     

Comparison of ventricular emptying with and without a pressure gradient in patients with hypertrophic cardiomyopathy

Thirty three patients with hypertrophic cardiomyopathy were studied to determine whether the presence of an intraventricular pressure gradient impaired left ventricular emptying. Patients with resting gradients had a higher mean left ventricular ejection fraction (92 (6.4)%) than patients without a resting or inducible pressure gradient (75.5 (9)%). The rate and degree of emptying increased when gradients greater than 85 mm Hg were induced in two patients with insignificant mitral regurgitation. If the induced gradients had been the result of obstruction a decrease in the rate or degree of ventricular emptying would be expected. Higher ejection fractions in patients with intracavitary pressure gradients as well as enhanced rate and degree of left ventricular emptying with induced gradients are inconsistent with outflow obstruction. These findings support the concept that cavity obliteration is responsible for the pressure gradient in these patients with hypertrophic cardiomyopathy.     

肥厚型心肌病患者小动脉弹性指数水平与左心室流出道梗阻的关系

目的：探讨肥厚型心肌病（HCM）患者小动脉弹性指数（C2）水平与左心室流出道梗阻的关系. 方法：纳入2010年1月至2013年7月间因肥厚型心肌病于我院心内科住院的患者69例,收集相关临床资料,比较C2水平与相关指标的关联性.再根据左心室流出道梗阻情况的不同,将HCM患者分为梗阻性HCM与非梗阻性HCM,比较两组患者的C2水平. 结果：N末端B型利钠肽原（NT-proBNP）、左室流出道最大压差（LVOTPG）与C2呈显著负相关,左室短轴缩短率（LVFS）与C2呈显著正相关,左室后壁宽度（LVPWD）与C2无显著相关性,超敏肌钙蛋白I（c-TNI）、左室射血分数（LVEF）、左室舒张末期内径（LVEDD）与C2呈非线性相关.梗阻性HCM患者的C2水平显著低于非梗阻性HCM患者. 结论：C2与LVOTPG密切相关,该指标可作为HCM患者左心室流出道梗阻病情进展的动态评价指标.     

肥厚性心肌病心衰患者左室流出道压差和运动心肺功能研究

目的：通过多巴酚丁胺负荷超声心动图和心肺运动联合试验（CPET）评价左室射血分数正常的心肌肥厚病临床心衰患者左室流出道（LVOT）压差,心房大小和运动心肺功能变化。方法：对35例正常人,62例梗阻型肥厚性心肌病（HCM）心衰患者进行多巴酚丁胺负荷脉冲型,连续波型,彩色多普勒超声心动图和CPET。测定LVOT压差,左房内径,于运动前、运动高峰和运动后分别测定峰氧耗量,无氧代谢阈（AT）,每分通气量/二氧化碳排出量（.VE/.VCO2）斜率。结果：与正常人相比较,LVOT梗阻的HCM心衰组患者左室短轴缩短率[（31±9）%∶（37±11）%]明显增大、LVOT压差[静态（3.9±1.1）mmHg∶（64±36）mmHg,负荷（13±7）mmHg∶（132±34）mmHg]明显增加、左房内径[（3.0±0.6）cm∶（4.3±0.7）cm]明显增大、A峰[（55±18）cm/s∶（81±35）cm/s]明显增高,峰值耗氧量[（32±7.9）ml/kg/min∶（18.4±5.8）ml/kg/min]、无氧阈（.VO2AT）[（16.5±2.1）ml/kg/min∶（9.2±2.2）ml/kg/min]明显下降,.VE/.VCO2斜率[（25.7±4.0）∶（32.8±5.1）]显著增加,P〈0.05~0.01。结论：左室流出道梗阻型肥厚性心肌病心衰患者,心房和心肺运动功能有明显改变。负荷超声和心肺运动联合试验有助于评价梗阻型肥厚性心肌病心衰患者左室流出道压差和运动时心肺功能。     

The prognostic importance of left ventricular outflow obstruction in hypertrophic cardiomyopathy varies in relation to the severity of symptoms

OBJECTIVES: The aim of this study was to investigate whether the prognostic importance of left ventricular (LV) outflow obstruction in hypertrophic cardiomyopathy (HCM) is influenced by other predictors of morbidity and mortality. BACKGROUND: It remains unknown whether the effect of outflow obstruction on clinical outcome in HCM is influenced by other determinants of survival. METHODS: We assessed the impact of severity of symptoms, LV wall thickness, atrial fibrillation, and age on the prognostic importance of outflow obstruction in a large HCM population. RESULTS: Of 526 consecutive HCM patients, 141 (27%) had outflow obstruction. During a follow-up of 4.5 +/- 4.1 years, 34 patients died of HCM. The incidence of cardiovascular death was significantly higher among patients with LV obstruction than among those without obstruction (relative risk [RR] = 2.14; p = 0.02). The prognostic power of the outflow gradient changed in relation to severity of symptoms (p = 0.024). At initial evaluation, LV obstruction was a significant predictor of cardiovascular mortality only in New York Heart Association (NYHA) functional class I to II patients (hazard ratio [HR] = 2.38; p = 0.025). During follow-up, at time of development of severe symptoms, the outflow gradient lost its prognostic significance (HR = 1.18; p = 0.66), whereas NYHA functional class III to IV was associated with an eight-fold increase in risk of cardiovascular mortality (HR = 7.90; p < 0.001). CONCLUSIONS: In patients with HCM, the prognostic importance of LV outflow obstruction varies in relation to the severity of symptoms. In patients with mild or no symptoms, obstruction is an important predictor of cardiovascular death. After development of severe symptoms, NYHA functional class becomes the dominant marker of prognosis independently of the presence of an outflow gradient.     

Relationship between outflow obstruction and left ventricular functional impairment in hypertrophic cardiomyopathy: a Doppler echocardiographic study

Left ventricular outflow tract (LVOT) obstruction is predictive of a worse outcome in hypertrophic cardiomyopathy (HCM). In a detailed Doppler echocardiographic study of 178 selected HCM patients, the group of patients (n = 73) with the obstructive form (resting peak gradient > or = 30 mmHg) presented more hypertrophy and poorer systolic and diastolic left ventricular (LV) functions than the HCM group (n = 105) without obstruction. LVOT peak gradient was positively correlated with hypertrophy (P < 0.0001) and negatively to tissue Doppler mitral annulus systolic (P = 0.0001) and early diastolic (P < 0.0001) velocities. The gradient significantly correlated with E/Ea ratio (r = 0.67; P < 0.0001). By multiple regression, LVOT gradient was related to E/Ea, LV maximal thickness and left atrial size. In comparison with patients without obstruction, patients with obstruction presented greater hypertrophy (P < 0.0001), lower systolic and early diastolic mitral annulus velocities (both P < 0.0001), higher E/Ea ratio (P < 0.0001) and higher global function index (P < 0.0001). In HCM, beyond the effects on hypertrophy, LVOT obstruction is an independent determinant of LV functional abnormalities.     

Impact of dual-chamber permanent pacing in patients with obstructive hypertrophic cardiomyopathy with symptoms refractory to verapamil and beta-adrenergic blocker therapy.

BACKGROUND. Patients with obstructive hypertrophic cardiomyopathy (HCM) with symptoms refractory to drugs (beta-blockers or verapamil) are candidates for cardiac surgery (left ventricular septal myectomy or mitral valve replacement). The present study examines prospectively the ability of dual-chamber (DDD) pacing to improve symptoms and relieve left ventricular outflow obstruction in such patients. METHODS AND RESULTS. Forty-four consecutive patients with obstructive HCM who had failed to benefit from pharmacotherapy underwent treadmill exercise tests, echocardiography, and cardiac catheterization before and 1.5-3 months after implantation of a DDD pacemaker. Symptoms (angina, dyspnea, palpitations, presyncope, and syncope), New York Heart Association functional class status (1.7 +/- 0.7 versus 3.4 +/- 0.5, p less than 0.00001), and exercise durations were improved at follow-up evaluation. This was associated with significant reduction in left ventricular outflow tract gradient (38 +/- 38 versus 87 +/- 43 mm Hg, p less than 0.0001) and significant increases in cardiac output and systemic arterial pressures. Notably, when pacing was discontinued and comparisons were made in sinus rhythm, treadmill exercise durations were greater and left ventricular outflow tract gradients were less at the follow-up evaluation compared with the baseline study. CONCLUSIONS. DDD pacing is an effective alternative to surgery in most patients with obstructive HCM with drug-refractory symptoms. The beneficial effects of pacing continue to be evident when pacing is acutely discontinued.