The significance of systolic anterior motion (SAM) on the mitral valve echo pattern in hypertrophic cardiomyopathy

Doppler color flow mapping studies of jet formation and spatial orientation in obstructive hypertrophic cardiomyopathy

To help clarify the mechanism of outflow tract obstruction and systolic anterior motion of the anterior leaflet of the mitral valve and their relation to the geometry of the left ventricle, we studied left ventricular outflow tract flow in 20 patients with hypertrophic cardiomyopathy (HCM) using two-dimensional Doppler flow mapping. We compared our results with outflow tract flow in 10 patients with isolated valvular aortic stenosis, (AS) and with those in 10 healthy volunteers. In HCM, a 94- to 145-degree angle (mean 111.4 +/- 11.9 degrees) developed between the direction of left ventricular outflow tract flow acceleration and aortic valve outflow, resulting in posterolaterally directed left ventricular outflow jets. The angle of the outflow jet and the peak velocity of the jet measured with continuous wave Doppler (as an indicator of the severity of obstruction) correlated well (r = -0.81, SEE = 7.8 degrees). Jet narrowing during ejection measured just proximal to the point of systolic anterior motion was 42 +/- 11% in HCM and was weakly correlated with peak jet velocity (r = 0.61, SEE = 8.9 degrees). Aliasing of left ventricular outflow occurred proximal to systolic anterior motion of the mitral valve, and color M-mode demonstrated temporal and spatial flow acceleration proximal to systolic anterior motion, providing evidence for obstruction at that site. In AS, left ventricular outflow tract jets were more parallel to the axis of aortic outflow (129 to 153 degree, 138.4 +/- 8.1 degrees). Jet narrowing was only 8 +/- 5% compared to HCM (both p less than 0.05), and flow acceleration occurred proximal to the stenotic valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertrophic cardiomyopathy. The importance of the site and the extent of hypertrophy. A review

Hypertrophic cardiomyopathy is a diverse clinical and pathophysiologic entity that involves principally the left ventricle and is caused by asymmetric or concentric hypertrophy of unknown cause. If asymmetric, the hypertrophy is usually greatest in the ventricular septum, but variations occur in which the hypertrophy may be maximal at the apex, at the midventricular level, or, rarely, in the free wall of the left ventricle. Right ventricular involvement is usually less evident. The principal abnormality in systole is the obstruction to left ventricular outflow caused by upper septal hypertrophy narrowing the outflow tract and setting the stage for Venturi forces to cause systolic anterior motion of the anterior or posterior mitral leaflets. The time of onset and duration of mitral leaflet-septal contact determine the magnitude of the pressure gradient. Mitral regurgitation invariably accompanies the obstruction to outflow. Ventriculomyotomy-myectomy surgery, by thinning the septum and widening the outflow tract, abolishes the abnormal mitral leaflet motion and, consequently, the obstruction to outflow and the mitral regurgitation. This form of surgery more dramatically relieves the systolic abnormalities and the accompanying symptoms than any form of medical therapy available today. The extent of hypertrophy is believed to be the principal determinant of the impaired left ventricular relaxation and increased chambers stiffness (decreased compliance) that characterize diastole in hypertrophic cardiomyopathy. Relaxation is impaired by the contraction load (the obstruction), by a decrease in the principal relaxation loads, by a pathologic degree of nonuniformity of contraction and relaxation, and in all likelihood, by impaired inactivation of the biochemical processes responsible for contraction (? due to primary or ischemia-induced calcium overload). Calcium channel-blocking agents may dramatically improve left ventricular relaxation by speeding up the inactivation process, by decreasing the degree of nonuniformity, or by altering the contraction and relaxation loads in a favorable manner. Atrial and ventricular arrhythmias are responsible for a significant proportion of the morbidity and mortality, and their occurrence also appears to depend on the extent of hypertrophy. Thus, the major manifestations of hypertrophic cardiomyopathy in systole and diastole as well as the disturbances of rhythm appear to be related to the site and/or extent of the hypertrophic process.(ABSTRACT TRUNCATED AT 400 WORDS)

An evaluation of two-dimensional echocardiography in the diagnosis of hypertrophic cardiomyopathy

Various anatomical and functional features of hypertrophic cardiomyopathy are analyzed in view of the data provided by two-dimensional echocardiography. Measurement of septal thickness is crucial, and is best done by a combination of M-Mode and 2-D echo. Two types of systolic anterior movement of the mitral valve (SAM) are observed and are related to the degree of subvalvular gradient. The specificity of these patterns of SAM is analyzed. The functional anatomy of the mitral valve in relation to the presence and degree of mitral regurgitation shows that although the presence and type of SAM are important, there are other causes of mitral regurgitation in hypertrophic cardiomyopathy unrelated to SAM. We emphasize the fact the 2-D echo cannot "diagnose" hypertrophic cardiomyopathy except when cardiac hypertrophy plus SAM involving the body of the mitral valve is seen; in the remaining cases, 2-D echo confirms/suggests the clinical diagnosis.

Patterns of systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy: Assessment by two-dimensional echocardiography

A variety of patterns of systolic anterior motion (SAM) of the mitral valve were identified by realtime, 2-dimensional echocardiography in 62 patients with hypertrophic cardiomyopathy. In 36 patients (58%), both the anterior and posterior mitral leaflets appeared to participate importantly in SAM, although the anterior leaflet actually contacted or most closely approached the ventricular septum during systole because of its anterior anatomic position. In 19 patients (31%), SAM was produced selectively by the posterior mitral leaflet. In only 6 patients (10%) was the anterior leaflet alone responsible for SAM. In just 1 patient did the chordae tendineae appear to be primarily responsible for the SAM. In 51 patients (82%), only the distal portion of the anterior or posterior mitral leaflet (and possibly the attached proximal chordae tendineae) approached or contacted the septum in systole; in 10 patients both the body and tip regions of the anterior leaflet produced mitral-septal apposition. Hence, in obstructive hypertrophic cardiomyopathy, (1) the morphologic structures responsible for moderate to severe SAM are not identical in all patients, and a variety of patterns of SAM occur; (2) the posterior mitral leaflet plays an important role in SAM in almost 90% of patients, either by producing SAM alone (31%) or by moving anteriorly in concert with the anterior leaflet (58%); (3) SAM produced selectively by the anterior mitral leaflet is relatively uncommon; and (4) SAM is usually produced primarily by the distal portions of the mitral leaflets (with or without the attached chordae tendineae).

Systolic anterior motion of the posterior mitral leaflet: a previously unrecognized cause of dynamic subaortic obstruction in patients with hypertrophic cardiomyopathy

Dynamic obstruction to left ventricular outflow in patients with hypertrophic cardiomyopathy usually occurs when the anterior mitral leaflet moves forward in systole and approaches or contacts the ventricular septum. However, we have recently identified, by M mode and two-dimensional echocardiography, 21 patients with hypertrophic cardiomyopathy who had a unique pattern of mitral valve motion characterized by abnormal mitral valve coaptation and systolic anterior motion of the posterior mitral leaflet. This abnormality of mitral valve motion was most reliably identified with two-dimensional echocardiography in views of the left ventricle obtained from the apex. At end-diastole the anterior and posterior mitral leaflets did not appear to coapt at their distal free margins. Rather, at mitral valve closure, the anterior mitral leaflet contacted the basal portion of posterior mitral leaflet. Subsequently, during systole the "residual" distal portion of posterior mitral leaflet approached or contacted the ventricular septum. Morphologic observations in nine other patients with hypertrophic cardiomyopathy suggested that systolic anterior motion of the posterior mitral leaflet is due to elongation of the middle scallop of the posterior leaflet, which probably comes into apposition with the ventricular septum during systole by passing through the space created by the normal pattern of chordal attachments onto the anterior mitral leaflet. Of the 16 patients who underwent cardiac catheterization, nine had basal subaortic gradients of 20 to 85 mm Hg, which were apparently due to moderate or marked systolic anterior motion of the posterior mitral leaflet. Ventricular septal myotomy-myectomies were performed in two patients and resulted in markedly diminished systolic anterior motion of the posterior mitral leaflet in each and abolition of subaortic gradient in the one patient who underwent postoperative cardiac catheterization. Hence, in patients with hypertrophic cardiomyopathy, systolic anterior motion of the posterior mitral leaflet (1) is not uncommon (identifiable in about 10% of a consecutively studied series of patients), (2) constitutes a previously undescribed mechanism for dynamic subaortic obstruction, and (3) is due to a malformation of the posterior mitral leaflet.

Mitral regurgitation in hypertrophic cardiomyopathy. Non-invasive study by two dimensional Doppler echocardiography

Mitral regurgitation and its haemodynamic features were investigated non-invasively in cases of hypertrophic cardiomyopathy by means of two dimensional Doppler echocardiography. There were 28 patients, 14 of whom showed systolic anterior motion (SAM) of the mitral echo; the other 14 did not. The following results were obtained. (1) Mitral regurgitation was detected by the Doppler technique in all cases with systolic anterior motion of the mitral echo and in half of those without it. (2) Doppler signals of mitral regurgitation started immediately after the first heart sound. (3) Mitral regurgitant flow was often distributed from the entire mitral orifice over the entire or the posterior half of the left atrium in the cases with systolic anterior motion. In the cases without systolic anterior motion the regurgitation was usually localised near the mitral orifice. These features differ from those of regurgitation usually seen in rheumatic mitral valve disease and idiopathic mitral valve prolapse. (4) The Doppler technique and left ventriculography were equally efficient in detecting mitral regurgitation. (5) The early systolic component of the murmur of hypertrophic myopathy is considered to result in the main from concomitant mitral regurgitation, but not from turbulent blood flow in the left ventricular outflow tract, so that in cases with mitral regurgitation as a complication, mitral regurgitation may also contribute to the development of the midsystolic portion of the systolic murmur, while the main origin of this portion of the murmur is the left ventricular outflow obstruction.

Cardiomyopathy: how far have we come in 25 years, how far yet to go?

Twenty-five years ago clinical investigators began to appreciate that cardiomyopathy is an important and reasonably common form of heart disease. Since then, several functional classifications have been proposed, the specific myocardial diseases have been classified and chronic ischemic ventricular failure has been described. The boundary separating myocarditis from dilated cardiomyopathy remains hazy and, despite intensive research, the causes of dilated cardiomyopathy remain obscure. In particular, we still do not understand the role that may be played by viral infection and alcohol. Myocardial biopsy has proved useful in patients with specific myocardial disorders, heart transplant recipients and patients receiving Adriamycin, but is disappointing in patients with dilated cardiomyopathy. It has become increasingly evident that exercise capacity does not correlate with ventricular function, being highly dependent on peripheral factors. Measurements of oxygen consumption during exercise promise to be useful in assessing treatment of dilated cardiomyopathy. True restrictive cardiomyopathy is uncommon, and the term should be reserved for cardiomyopathies that meet strict criteria. A restrictive component to filling is common to many cardiac disorders, including some cases of cardiac amyloidosis. The concept of hypertrophic cardiomyopathy has evolved rapidly over the past 25 years, and continues to evolve. The importance of arrhythmia as a cause of sudden death is becoming increasingly clear. The place of calcium channel blocking agents in the treatment of hypertrophic cardiomyopathy will probably emerge soon. Amiodarone is finding an increasing role in the treatment of dilated and hypertrophic cardiomyopathy. Surgical treatment is still required for some patients despite unanswered questions on how it works.

The frontiers of cardiomyopathy

Images

Abnormal mitral valve coaptation in hypertrophic obstructive cardiomyopathy: proposed role in systolic anterior motion of mitral valve

Two dimensional echocardiographic evaluation utilizing the apical four chamber and apical long axis views was made in 10 normal subjects and 35 patients with hypertrophic cardiomyopathy, including 16 without and 19 with systolic anterior motion of the mitral valve. Mitral valve leaflets were imaged throughout the cardiac cycle. The normal subjects and the patients with hypertrophic cardiomyopathy without systolic anterior motion demonstrated mitral valve coaptation that seemed to involve the distal tip of the anterior leaflet. In contrast, patients with hypertrophic cardiomyopathy with systolic anterior motion demonstrated abnormal coaptation, so that the posterior leaflet coapted with a mid portion of the anterior leaflet, leaving a distal "residual" anterior leaflet in the left ventricle during systole. A sharp angulation of this distal leaflet in mid systole toward the interventricular septum is thought to represent systolic anterior motion. It is speculated that abnormal mitral leaflet coaptation in necessary for development of leaflet systolic anterior motion, which is correlated with dynamic left ventricular outflow gradients in hypertrophic obstructive cardiomyopathy.

Specificity of systolic anterior motion of anterior mitral leaflet for hypertrophic cardiomyopathy. Prevalence in large population of patients with other cardiac diseases

The value of systolic anterior motion of the anterior mitral leaflet as a diagnostic marker for hypertrophic cardiomyopathy has been questioned because of its reported occurrence in other heart diseases. To determine the true specificity of systolic anterior motion for hypertrophic cardiomyopathy, 721 echocardiograms from patients with a wide variety of cardiac diseases were reviewed for its presence or absence under basal conditions. Systolic anterior motion of the anterior mitral leaflet was present in only 22 (3.0%) of the 721 patients, giving a specificity of 97 per cent. It was most common in patients with d-transposition of the great vessels (11 of 51, or 21%). With patients having transposition of the great vessels excluded from the analysis, the prevalence of systolic anterior motion of the anterior mitral leaflet was only 1.6 per cent (specificity 98%). Of note, eight of the 11 patients with systolic anterior motion of the anterior mitral leaflet and diseases other than transposition of the great vessels had disproportionate thickening of the ventricular septum, making it exceedingly rare in a patient population with normal septal-free wall thickness ratios (prevalence 0.4%; specificity 99%). Hence, while systolic anterior motion is not pathognomonic of hypertrophic cardiomyopathy, it was an uncommon finding in a large population of patients with a variety of cardiac diseases; when present in such patients systolic anterior motion of the anterior mitral leaflet is usually associated with disproportionate septal thickening.