Provocation of left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy

Several provocation maneuvers are described in hypertrophic cardiomyopathy to Doppler echocardiographically distinguish the obstructive from the non obstructive type. No data are available about the value of orthostasis testing in comparison with nitrate application in this disease. In this study, 16 consecutive patients with hypertrophic cardiomyopathy were examined. 11 patients with hypertrophic cardiomyopathy were classified as obstructive, 5 patients with hypertrophic cardiomyopathy as non obstructive. Normal left ventricular outflow tract velocities as detected by the Doppler method were defined as < 2,0 m/s.Doppler echocardiographic measurements were performed after 10 minutes in supine position, within 10 minutes after head-up tilt and again, within 10 minutes in supine position. If systolic blood pressure during this examination exceeded 100 mm Hg 2,5 mg isosorbiddinitrate were sprayed sublingually. Measurements were done after 20 minutes in supine position and within 10 minutes after head-up tilt.Only in 7 of the 11 patients with hypertrophic obstructive cardiomyopathy maximal left ventricular outflow tract velocity in supine position measured > 2,0 m/s (2,2 ± 0,8). During head-up tilt, all patients showed increased values (3,8 ± 1,2 m/s). No differences in maximal left ventricular outflow tract velocity between head-up tilt and nitrate application in supine position (3,5 ± 1,4 m/s) were present. All patients with hypertrophic non obstructive cardiomyopathy showed maximal left ventricular outflow tract velocities < 2,0 m/s in every step of the examination.Consequently, orthostasis testing was able to identify all patients with hypertrophic obstructive cardiomyopathy and demonstrated a diagnostic value similar to nitrate application.     

Left ventricular pulsus alternans in patients with hypertrophic cardiomyopathy and severe obstruction to left ventricular outflow

Left ventricular pulsus alternans (LVPA), a rhythmic beat to beat variation in left ventricular systolic pressure and outflow gradient, was noted in 35 of 200 ventricular systolic pressure and outflow gradient, was noted in 35 of 200 patients with hypertrophic cardiomyopathy undergoing hemodynamic study. LVPA was not associated with significant systemic pulsus alternans nor right ventricular pulsus alternans. All patients with LVPA had severe outflow gradients at rest or during provocation. Of 61 patients with severe basal outflow gradients (greater than 80 mm Hg), 12 demonstrated LVPA at rest. Eight of these patients underwent ventricular septal myotomy-myectomy; all had successful abolition of basal outflow gradient. Of the seven of these eight patients who underwent postoperative hemodynamic study and who were in sinus rhythm, none demonstrated LVPA. Eleven of 60 patients with basal outflow gradients ranging from 10 to 70 mm Hg demonstrated LVPA during maneuvers provocative for outflow gradients (mean gradient 90 +/- 37 mm Hg). Two of these patients underwent ventricular septal myotomy-myectomy; neither had a gradient nor LVPA during provocation postoperatively. Twelve additional patients with basal outflow gradients ranging from 0 to 115 mm Hg had LVPA after ectopic beats, generally occurring during maneuvers provocative for outflow gradients, associated with severe outflow gradients (mean gradient 130 +/- 39 mm Hg) during the postextrasystolic beat. None of the 41 patients without an outflow gradient, basal or during provocation, was found to have LVPA. Thus LVPA is commonly seen in during provocation, was found to have LVPA. Thus LVPA is commonly seen in patients with hypertrophic cardiomyopathy and severe left ventricular outflow gradients and may represent inadequate left ventricular contractile function in the presence of high left ventricular systolic pressures.     

Underappreciated occurrence of discrete subaortic membranes producing left ventricular outflow obstruction in hypertrophic cardiomyopathy

Subaortic obstruction due to systolic anterior motion (SAM) of the mitral valve with ventricular septal contact is a major cause of progressive heart failure symptoms in patients with hypertrophic cardiomyopathy (HCM). However, we have recently observed a unique, but not uncommon subgroup of HCM patients with outflow tract obstruction due only to discrete subaortic membrane or who have a membrane in addition to SAM‐septal contact. HCM patients with subaortic membranes may be at increased risk for developing progressive heart failure symptoms. Identification requires a high index of suspicion and raises important management considerations, including need for surgical myectomy for definitive relief of obstruction with associated excellent outcomes, as the alternative invasive treatment option with percutaneous alcohol septal ablation would be ineffective.     

Fixed left ventricular outflow tract obstruction mimicking hypertrophic obstructive cardiomyopathy: pitfalls in diagnosis

We present a case series that highlights the diagnostic challenges with left ventricular hypertrophy (LVH) and left ventricular outflow tract obstruction (LVOTO). Fixed structural lesions causing LVOTO with secondary LVH may mimic hypertrophic obstructive cardiomyopathy (HOCM). Management of these two entities is critically different. Misdiagnosis and failure to recognize fixed left ventricular outflow tract (LVOT) lesions may result in morbidity as a result of inappropriate therapy and delay of definitive surgical treatment. It is thus necessary to identify the correct type and level of obstruction in the LVOT by careful correlation of clinical examination, Doppler evaluation, and advanced imaging findings.     

Management of left ventricular outflow obstruction due to hypertrophic cardiomyopathy. Role of multimodality echocardiographic techniques

Hypertrophic cardiomyopathy is a diverse condition, encompassing a wide spectrum of clinical manifestations. Left ventricular outflow obstruction occurs in a proportion of patients, and is amenable to a variety of management strategies. Echocardiography plays a crucial role in the diagnosis of hypertrophic cardiomyopathy, and in the assessment of left ventricular outflow obstruction, as well the selection of appropriate therapy. In particular echocardiography is crucial in the selection, intraoperative monitoring and follow-up of patients suitable for alcohol septal ablation therapy. This article outlines the role of echocardiography in the assessment and management of left ventricular outflow obstruction in these patients.     

Development and determinants of dynamic obstruction to left ventricular outflow in young patients with hypertrophic cardiomyopathy.

BACKGROUND. To study the development of dynamic subaortic obstruction in young patients with hypertrophic cardiomyopathy (HCM), serial echocardiograms were retrospectively analyzed in a group of 26 consecutive children with this disease who showed no evidence of dynamic outflow obstruction at their initial evaluation (age, 11 +/- 3 years). METHODS AND RESULTS. After a follow-up of 3-12 years (mean, 7 +/- 3 years), seven of the 26 patients (27%) developed echocardiographic evidence of subaortic obstruction, i.e., marked systolic anterior motion (SAM) of the mitral valve with mitral-septal apposition and increased left ventricular outflow tract systolic velocities (3.8 +/- 0.3 m/sec; range, 3.1-4.5). Patients who developed SAM had smaller transverse dimension of the left ventricular outflow tract and more anteriorly displaced mitral valve when initially evaluated than did patients without development of SAM (outflow tract dimension, 19.1 +/- 4 versus 24.6 +/- 4 mm; mitral valve position index, 1.07 +/- 0.2 versus 0.73 +/- 0.3; each p less than 0.02). In patients with development of SAM, the already reduced outflow tract dimension decreased further during follow-up, and the mitral valve became even more anteriorly displaced within the left ventricular cavity. These developmental alterations in outflow tract size were associated with increases in left ventricular wall thickness, particularly of the basal anterior septum (11.0 +/- 8 mm; 72 +/- 33%) compared with control patients with HCM who did not develop SAM (3.0 +/- 3 mm; 17 +/- 10%; p less than 0.05). CONCLUSIONS. Development of subaortic obstruction in young patients with HCM results from a process of dynamic remodeling of left ventricular geometry over several years and is characterized by progressive narrowing of the outflow tract with anterior displacement of the mitral valve and disproportionate thickening of the basal anterior ventricular septum.     

Use of Doppler echocardiography and amyl nitrite inhalation to characterize left ventricular outflow obstruction in hypertrophic cardiomyopathy

The presence of left ventricular outflow tract obstruction (LVOTO) of either a resting or dynamic nature may have important therapeutic and prognostic implications in patients with hypertrophic cardiomyopathy (HCM). Doppler echocardiograms combined with amyl nitrite (Amyl) inhalation were performed in 333 consecutive patients referred for suspected HCM to diagnose and categorize the nature and severity of LVOTO. Hypertrophic cardiomyopathy was present by 2-D and M-mode criteria in 145/333 (44 percent) patients. Normal limits of resting and post-Amyl continuous wave Doppler peak left ventricular outflow tract velocities were established in 15 subjects with completely normal 2-D and Doppler echocardiograms. Based on these criteria, of the 145 patients with HCM, 63 (43 percent) were classified as having resting LVOTO, peak velocity 4.2 +/- 1.3 m/s. Among 82 patients with HCM without resting LVOTO, 47 (57 percent) received Amyl. Latent LVOTO was provoked in 25/47 (53 percent), peak post-Amyl velocity 4.5 +/- 1.2 m/s. The remaining 22 (47 percent) had nonobstructive HCM, as indicated by no significant increase in post-Amyl velocity. Among a total 62 subjects receiving Amyl, none experienced serious morbidity or mortality. Doppler echocardiography, in conjunction with Amyl inhalation in selected patients, is a useful noninvasive method to diagnose and categorize patients with HCM according to the nature and severity of LVOTO.     

Systole-diastole mismatch in hypertrophic cardiomyopathy is caused by stress induced left ventricular outflow tract obstruction

Background

Pharmacological stress is used to assess the degree of left ventricular (LV) subvalvular gradient in patients with hypertrophic cardiomyopathy (HCM), but there is little information about associated physiological changes.

Methods

Echocardiography-Doppler ultrasound scanning measurements in 23 patients with HCM and 23 control subjects of similar age were studied at rest and at the end point of dobutamine stress.

Results

In patients, the systolic time was normal at rest, but increased abnormally with stress. In patients, the total isovolumic contraction time failed to shorten, and the total ejection time increased abnormally. Changes in total ejection time correlated with an increase in peak subvalvular gradient in control subjects and patients (r = 0.52 and r = 0.66, respectively; P <.01 for both). In patients, the diastolic time was normal at rest, but shortened abnormally with stress. In patients, the isovolumic relaxation time fell abnormally, as did the filling time. Mitral E wave acceleration and left atrium size were unchanged with stress in control subjects, but consistently increased in patients with HCM, which indicates an increased early diastolic atrioventricular pressure gradient.

Conclusion

In HCM, systolic period increases abnormally with stress. This is not because of a loss of inotropy, but is directly related to the degree of LV outflow tract obstruction. As a result, the diastolic period fails to increase, reducing the time available for coronary flow, the LV filling pattern is modified, and the diastolic atrioventricular pressure gradient increases. These changes may contribute to symptom development and suggest why reducing LV outflow tract obstruction per se may be therapeutically useful in HCM.     

Effect of amiodarone-induced hyperthyroidism on left ventricular outflow obstruction after septal myectomy for hypertrophic cardiomyopathy

Patients with obstructive hypertrophic cardiomyopathy who undergo septal myectomy are at risk for developing postoperative atrial fibrillation. Amiodarone is effective in treating this arrhythmia but is associated with multiple adverse effects, often with delayed onset. A novel case is described of a patient who developed type 2 amiodarone-induced hyperthyroidism that presented as recurrence of outflow obstruction after septal myectomy. The patient's symptoms and echocardiographic findings of outflow obstruction resolved substantially with the treatment of the amiodarone-induced hyperthyroidism. Amiodarone-induced hyperthyroidism of delayed onset can be a subtle diagnosis, requiring a high index of suspicion. In conclusion, recognition of this diagnosis in patients with recurrence of outflow obstruction by symptoms and cardiac imaging after septal myectomy may avoid unnecessary repeat surgical intervention.     

Inspiratory right ventricular outflow obstruction in a patient with hypertrophic cardiomyopathy

A patient with familial hypertrophic cardiomyopathy with exertional near syncope is reported. Intra-right ventricular obstruction was demonstrated by hemodynamic studies during inspiration and the Valsalva maneuver with systemic hypotension. Improvement occurred following the administration of propranolol. It was suggested that syncope might be precipitated by hemodynamic changes such as a high output state and a depressed cardiac volume in relation to intra-right ventricular obstruction in patients with hypertrophic cardiomyopathy.