Has 'obstruction' hindered our understanding of hypertrophic cardiomyopathy?

Measurement of Turbulent Kinetic Energy in Hypertrophic Cardiomyopathy Using Triple-velocity Encoding 4D Flow MR Imaging

PURPOSE

The turbulent kinetic energy (TKE) estimation based on 4D flow MRI has been currently developed and can be used to estimate the pressure gradient. The objective of this study was to validate the clinical value of 4D flow-based TKE measurement in patients with hypertrophic cardiomyopathy (HCM).

METHODS

From April 2018 to March 2019, we recruited 28 patients with HCM. Based on echocardiography, they were divided into obstructed HCM (HOCM) and non-obstructed HCM (HNCM). Triple-velocity encoding 4D flow MRI was performed. The volume-of-interest from the left ventricle to the aortic arch was drawn semi-automatically. We defined peak turbulent kinetic energy (TKEpeak) as the highest TKE phase in all cardiac phases.

RESULTS

TKEpeak was significantly higher in HOCM than in HNCM (14.83 ± 3.91 vs. 7.11 ± 3.60 mJ, P < 0.001). TKEpeak was significantly higher in patients with systolic anterior movement (SAM) than in those without SAM (15.60 ± 3.96 vs. 7.44 ± 3.29 mJ, P < 0.001). Left ventricular (LV) mass increased proportionally with TKEpeak (P = 0.012, r = 0.466). When only the asymptomatic patients were extracted, a stronger correlation was observed (P = 0.001, r = 0.842).

CONCLUSION

TKE measurement based on 4D flow MRI can detect the flow alteration induced by systolic flow jet and LV outflow tract geometry, such as SAM in patients with HOCM. The elevated TKE is correlated with increasing LV mass. This indicates that increasing cardiac load, by pressure loss due to turbulence, induces progression of LV hypertrophy, which leads to a worse prognosis.

Ventricular tachycardia and heart failure in a patient of mid-ventricular obstructive hypertrophic cardiomyopathy with apical aneurysm: A case report

Mid-ventricular obstructive hypertrophic cardiomyopathy (MVOHC) with apical aneurysm is a rare type of cardiomyopathy. It is associated with an elevated risk of ventricular arrhythmias, thromboembolism, heart failure and sudden cardiac death. The present case study reports on a patient with MVOHC and apical aneurysm who developed ventricular arrhythmias and heart failure. The patient received an implantable cardioverter defibrillator for prevention of fatal arrhythmias. Ventricular tachycardia was terminated by increased doses of amiodarone and β-blocker. Transthoracic echocardiography indicated a mid-ventricular gradient of 64 mmHg. The patient refused surgical treatment and opted for alcohol septal ablation (ASA). At the 6-month follow-up, a rebound of the gradient following ASA was observed on echocardiography. In the present study, timely recognition of MVOHC with apical aneurysm led to prompt defibrillator implantation for prophylaxis regarding further malignant arrhythmias. Surgical management should be considered in symptomatic patients with MVOHC and apical aneurysm.

The 50-year history, controversy, and clinical implications of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy from idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy: from idiopathic hypertrophic subaortic stenosis to hypertrophic cardiomyopathy

Dynamic obstruction to left ventricular (LV) outflow was recognized from the earliest (50 years ago) clinical descriptions of hypertrophic cardiomyopathy (HCM) and has proved to be a complex phenomenon unique in many respects, as well as arguably the most visible and well-known pathophysiologic component of this heterogeneous disease. Over the past 5 decades, the clinical significance attributable to dynamic LV outflow tract gradients in HCM has triggered a periodic and instructive debate. Nevertheless, only recently has evidence emerged from observational analyses in large patient cohorts that unequivocally supports subaortic pressure gradients (and obstruction) both as true impedance to LV outflow and independent determinants of disabling exertional symptoms and cardiovascular mortality. Furthermore, abolition of subaortic gradients by surgical myectomy (or percutaneous alcohol septal ablation) results in profound and consistent symptomatic benefit and restoration of quality of life, with myectomy providing a long-term survival similar to that observed in the general population. These findings resolve the long-festering controversy over the existence of obstruction in HCM and whether outflow gradients are clinically important elements of this complex disease. These data also underscore the important principle, particularly relevant to clinical practice, that heart failure due to LV outflow obstruction in HCM is mechanically reversible and amenable to invasive septal reduction therapy. Finally, the recent observation that the vast majority of patients with HCM have the propensity to develop outflow obstruction (either at rest or with exercise) underscores a return to the characterization of HCM in 1960 as a predominantly obstructive disease.

Pathophysiology and Treatment of Hypertrophic Cardiomyopathy

All patients with hypertrophic cardiomyopathy (HCM) should have five aspects of care addressed. An attempt should be made to detect the presence or absence of risk factors for sudden arrhythmic death. If the patient appears to be at high risk, discussion of the benefits and risks of ICD are indicated, and many such patients will be implanted. Symptoms are appraised and treated. Bacterial endocarditis prophylaxis is recommended. Patients are advised to avoid athletic competition and extremes of physical exertion. First degree family members should be screened with echocardiography and ECG.

Effect of left ventricular outflow tract obstruction on clinical outcome in hypertrophic cardiomyopathy

BACKGROUND

The influence of left ventricular outflow tract obstruction on the clinical outcome of hypertrophic cardiomyopathy remains unresolved.

METHODS

We assessed the effect of outflow tract obstruction on morbidity and mortality in a large cohort of patients with hypertrophic cardiomyopathy who were followed for a mean (+/-SD) of 6.3+/-6.2 years.

RESULTS

Of the 1101 consecutive patients, 273 (25 percent) had obstruction of left ventricular outflow under basal (resting) conditions with a peak instantaneous gradient of at least 30 mm Hg. A total of 127 patients (12 percent) died of hypertrophic cardiomyopathy, and 216 surviving patients (20 percent) had severe, disabling symptoms of progressive heart failure (New York Heart Association [NYHA] functional class III or IV). The overall probability of death related to hypertrophic cardiomyopathy was significantly greater among patients with outflow tract obstruction than among those without obstruction (relative risk, 2.0; P=0.001). The risk of progression to NYHA class III or IV or death specifically from heart failure or stroke was also greater among patients with obstruction (relative risk, 4.4; P<0.001), particularly among patients 40 years of age or older (P<0.001). Age-adjusted multivariate analysis confirmed that outflow tract obstruction was independently associated with an increased risk of both death related to hypertrophic cardiomyopathy (relative risk, 1.6; P=0.02) and progression to NYHA class III or IV or death from heart failure or stroke (relative risk, 2.7; P<0.001). The likelihood of severe symptoms and death related to outflow tract obstruction did not increase as the gradient increased above the threshold of 30 mm Hg.

CONCLUSIONS

In patients with hypertrophic cardiomyopathy, left ventricular outflow tract obstruction at rest is a strong, independent predictor of progression to severe symptoms of heart failure and of death.

Comparison of dual-chamber pacing versus septal myectomy for the treatment of patients with hypertrophic obstructive cardiomyopathy: a comparison of objective hemodynamic and exercise end points

OBJECTIVES

The purpose of this study was to compare the treatment effects of septal myectomy with dual-chamber pacing in patients with hypertrophic obstructive cardiomyopathy (HOCM).

BACKGROUND

The optimal treatment for symptomatic patients with drug-refractory HOCM is unknown. Both dual-chamber pacing and surgical myectomy may result in subjective symptom improvement. However, no direct comparisons with objective end points have been reported.

METHODS

Thirty-nine patients with symptomatic HOCM were analyzed in this concurrent cohort study. Twenty patients underwent surgical myectomy, and 19 received dual-chamber pacemakers based on patient preference. These patients had prospective baseline and follow-up evaluations including physician assessment, echocardiography and standardized metabolic treadmill exercise testing.

RESULTS

Baseline symptom status, left ventricular outflow tract gradients, exercise times and maximal oxygen consumption peak were similar between the two groups. Left ventricular outflow gradient was reduced from 76+/-57 to 9+/-17 mm Hg (p = 0.0001) after myectomy, and from 77+/-61 to 55+/-39 mm Hg (p = 0.07) after pacing (p = 0.02 for comparison with myectomy). Ninety percent of myectomy patients experienced symptomatic improvement as compared with 47% in the pacing group. Exercise duration increased significantly from 6.6+/-2.8 to 8.7+/-3.0 min (p = 0.0003) after myectomy compared with a change from 6.4+/-2.1 to 7.0+/-2.2 min (p = NS) in the pacing group. Maximal oxygen consumption increased from 19.4+/-6.4 to 22.2+/-6.5 ml/kg/min after myectomy (p = 0.004), whereas the pacing group did not experience any significant change (19.6+/-6.5 vs. 20.1+/-6.5 ml/kg/min, p = NS).

CONCLUSIONS

Surgical myectomy and dual-chamber pacing improve subjective measures of functional status in patients with symptomatic HOCM. In this nonrandomized study, myectomy offered greater reduction in left ventricular outflow tract gradients and larger improvements in objective measures of patient symptoms and functional status when compared with dual-chamber pacing.

Dual-chamber pacing for cardiomyopathies: a 1996 clinical perspective

Implantation of a permanent pacemaker is an accepted mode of therapy for symptomatic bradyarrhythmias. Application of pacemaker technology for the treatment of cardiomyopathies has generated considerable interest and enthusiastic support in recent years. In both hypertrophic cardiomyopathy and dilated cardiomyopathy, dual-chamber pacing has been shown to decrease symptoms and improve hemodynamics; however, not all patients will benefit from dual-chamber pacing. Technical considerations must be acknowledged in order to obtain optimal benefit with dual-chamber pacing. In addition, other more accepted therapies are available for patients with symptomatic cardiomyopathies. The purposes of this article are to review critically the current literature on the use of dual-chamber pacemakers in patients with either hypertrophic or dilated cardiomyopathy and to provide a clinical perspective based on current knowledge.

A three-dimensional computational investigation of intraventricular fluid dynamics: examination into the initiation of systolic anterior motion of the mitral valve leaflets

Systolic anterior motion of the mitral valve leaflets (SAM) is a disease of the left ventricle which results from an abnormal force balance on the mitral valve. The mechanism by which is initiated is poorly understood, and a complete understanding of this mechanism is required for effective treatment of SAM. There are currently two theories for the initiation mechanism of SAM, the Venturi hypothesis and the altered papillary muscle-mitral valve geometry theory (PM-MV). The Venturi hypothesis states that abnormally high ejection velocities create Venturi forces which initiate SAM. The PM-MV theory asserts that SAM is the result of abnormally distributed chordal forces which are incapable of preventing SAM. To investigate the initiation mechanism of SAM, a computer model of early systolic flow in an anatomically-correct human left ventricle was developed using Peskin's immersed boundary algorithm. The computer model was used to determine the effect of chordal force distribution and septal thickness of the intraventricular flow field. The results show that the degree of SAM is inversely proportional to the amount of chordal restraint applied to the central portion of the leaflets. Also, the results support the PM-MV theory and indicate the following: (i) fluid forces capable of initiating SAM as always present in a normal human ventricle; (ii) SAM does not occur normally because of the presence of chordal forces on the central portion of the mitral leaflet; (iii) SAM will occur when these central chordal forces are sufficiently low; (iv) the extent of SAM is inversely proportional to these central chordal forces; and (v) Venturi forces alone can not cause SAM.

Clinical assessment of ventricular ejection dynamics with and without outflow obstruction

With the advent of multisensor micromanometric/velocimetric catheterization, digital angiography and Doppler and color echocardiography, extensive fluid dynamic quantitation is now possible in cardiology. Such high fidelity instantaneous measurements offer the clinician the prospect of identifying phasic changes in ventricular ejection dynamics that may disclose contraction abnormalities before overt muscle or pump failure is manifested. Accordingly, this review provides a basis for interpreting these measurements and a conceptual framework for understanding ventricular ejection dynamics with and without outflow obstruction. Necessary terminology and fluid dynamic background, including properties of flows generated by large transient forces, Euler and unsteady Bernoulli equations and local and convective acceleration gradients, are reviewed first. Physiologic aspects of ejection dynamics and transvalvular and intraventricular gradients without obstruction are discussed. Maximal outflow acceleration, rather than ejection velocity, coincides with the attainment of the early peak of the nonobstructive pressure gradients. These gradients are characteristically even more asymmetric than are the associated ejection velocity signals. Clinical correlations are introduced, beginning with obstructive transvalvular and subvalvular gradients in aortic stenosis and the phenomenon of recovery of pressure loss in the poststenotic dilation. The large obstructive gradients tend to be distinctively symmetric, as are the ejection waveforms, whose configuration they track more or less closely, depending on the degree of stenosis and relative preponderance of convective effects throughout ejection. Pitfalls in some unwarranted applications of the "simplified Bernoulli equation" are pointed out. Polymorphic gradients of hypertrophic cardiomyopathy, reflecting dynamically dissimilar intraventricular flow regimes in early, mid and late systole, are examined. Enormous late systolic gradients can be associated with progressive shrinkage of flow passage area and sharp increases in linear velocity while volumetric outflow is diminutive. The concept of ventriculoannular disproportion in dilated ventricles is defined and discussed. The implications of ejection fluid dynamics for systolic ventricular and myocardial loading are examined, and the concept of complementarity and competitiveness between intrinsic and extrinsic load components is introduced. Finally, critical research issues are identified and addressed. The primary emphasis is on using the basic principles of fluid dynamics to better understand ejection in the normal or abnormal human left ventricle and aortic root.(ABSTRACT TRUNCATED AT 400 WORDS)

The significance of increased left ventricular outflow tract velocities in the elderly measured by continuous wave Doppler

Forty-four elderly patients (mean age 80 +/- 7 years) with elevated left ventricular outflow tract velocities and corresponding outflow tract gradients documented by continuous wave Doppler are reported (mean peak gradient 50 +/- 28). They had severe left ventricular hypertrophy, small left ventricular end-diastolic dimensions, and supernormal ejection fractions. Thirty-nine percent had a history of hypertension. They were predominantly female, had uniform concentric left ventricular hypertrophy, and had a high incidence of congestive heart failure. Diastolic function was found to be reduced in the elderly group compared to young patients with hypertrophic cardiomyopathy and to age- and sex-matched normal controls. It is concluded that most elderly patients with increased left ventricular outflow tract velocities are etiologically distinct from young patients with hypertrophic cardiomyopathy.

The challenge of cardiomyopathy

The combined clinical and pathophysiologic characteristics and diagnostic features as well as current concepts of pathogenesis, therapy and prevention of the principal forms of cardiomyopathy are reviewed. These include hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy and specific cardiac muscle disease. Emphasis is placed on recent developments and unresolved questions requiring application of newer techniques of molecular biology and genetics and adult myocyte culturing.

Causal relation between the pressure gradient and left ventricular ejection time in hypertrophic cardiomyopathy

This study was designed to evaluate the relation between severity of obstruction to left ventricular outflow and left ventricular ejection time in hypertrophic obstructive cardiomyopathy. With dual catheters across the left ventricular outflow tract, the pressure gradient and corresponding left ventricular ejection time were measured in 10 patients as the pressure gradient was pharmacologically provoked or abolished, or both. The patients were studied during constant atrial pacing to avoid the potential errors introduced with heart rate correction equations. The pressure gradient was pharmacologically provoked or reduced over a range of greater than or equal to 62 mm Hg per patient. In each patient the left ventricular ejection time varied directly with the pressure gradient (mean r = 0.97, range 0.92 to 1.00). The change in magnitude of the pressure gradient varied directly with the corresponding change in the measured ejection time (mean r = 0.98, range 0.97 to 1.00). When the data from all 10 patients were pooled with use of Weissler's heart rate correction equation, the relation between the corrected left ventricular ejection time and the pressure gradient was still significant and linear (r = 0.86), but less so than in individual patients. This difference was the result of marked interpatient variability in the slope of this linear relation reflecting interpatient differences in other important factors, such as underlying myocardial contractility and stroke volume, that influence left ventricular ejection time. This study demonstrates a clear, direct and highly significant relation between the magnitude of the pressure gradient and the left ventricular ejection time in hypertrophic obstructive cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Isoproterenol induction of vasodepressor-type reaction in vasodepressor-prone persons

The ability of isoproterenol to induce symptoms and laboratory findings of a vasodepressor reaction was tested in 48 patients, ages 17 to 74, divided into 4 groups according to the reason for their referral. Group 1 comprised 12 patients with vasodepressor syncope, group 2 had 8 patients with syncope of unknown origin, group 3 included 11 patients with syncope due to seizures in 2 and ventricular tachycardia in 9, group 4 had 17 patients with various arrhythmias not associated with syncope. Isoproterenol boluses were administered starting at 2 micrograms and increased in 2-micrograms steps to a maximum of 8 micrograms at 0 degree and +60 degrees. The responses at 0 degrees were all normal. At +60 degrees a vasodepressor reaction consisting of syncope or near syncope, hypotension and bradycardia was produced by isoproterenol (mean dose 6.0 +/- 0.26 micrograms) in 8 patients from group 1 (66.6%), 4 from group 2 (50%), 0 from group 3 and 4 from group 4 (23.5%). Three of the 4 patients in group 4 had a remote history of classic vasodepressor syncope. The overall sensitivity and specificity of the test were 73 and 85%, respectively, while the predictive accuracy of a test with positive or negative outcome were 69 and 89%, respectively. Muscarinic receptor blockade with atropine in 4 patients prevented isoproterenol-induced bradycardia but not hypotension or symptoms of fainting. Beta-adrenergic receptor blockade with propranolol inhibited all aspects of the isoproterenol-induced faint. Thus, the administration of isoproterenol during a passive upright tilt may identify persons who suffer from or are prone to a vasodepressor reaction.

Doppler evidence that true left ventricular-to-aortic pressure gradients exist in hypertrophic cardiomyopathy

The etiology of systolic left ventricular-to-aortic pressure gradients in hypertrophic cardiomyopathy is still controversial. While cavity obliteration has been proposed by some investigators as the cause for recording of a high left ventricular systolic pressure, the concept of left ventricular outflow tract obstruction has received more experimental support. To investigate further whether left ventricular pressure truly exceeds aortic pressure and implies obstruction, we studied, with imaging and Doppler echocardiographic techniques, five patients with asymmetric septal hypertrophy and systolic anterior movement of the mitral valve occasionally causing it to abut upon the septum. All had outflow tract pressure gradients (peak 85 +/- 10 mm Hg) and trace to mild mitral regurgitation. Continuous wave Doppler study recorded peak flow velocities in the outflow tract (4.6 +/- 0.3 m/sec), and mitral regurgitant (mean 6.6 +/- 0.3 m/sec) jets. Aortic systolic and diastolic blood pressures were measured by cuff sphygmomanometry, and simultaneous carotid pulse tracings were recorded. The magnitude of systolic aortic pressure was determined at the time of peak velocity in the mitral regurgitant jet. Since the peak systolic pressure gradient across the mitral valve (left ventricular minus left atrial pressure) should equal 4 times the square of the peak velocity (V) in the mitral regurgitant jet, peak left ventricular systolic pressure should equal 4 x V2 plus the height of left atrial pressure at the time of peak mitral regurgitant velocity. In each case, calculations were made assuming an upper normal left atrial pressure of 10 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased intensity of the murmur of hypertrophic obstructive cardiomyopathy with carotid sinus pressure

In a prospective study murmurs increased in intensity with carotid sinus pressure in 18 of 26 patients with hypertrophic obstructive cardiomyopathy (HOCM) (sensitivity, 69.2 percent for the 26 patients, 85.7 percent for the 21 patients in whom heart rate and blood pressure decreased with carotid sinus pressure). On the other hand, the murmur remained constant or decreased in all but one of 104 patients with valvular aortic stenosis, mitral insufficiency, hypertrophic nonobstructive cardiomyopathy, and systolic murmurs of miscellaneous origins (specificity, 99 percent; positive predictive value, 94.7 percent). Catheterization, indirect arterial pressure tracings, and echocardiographic studies indicated that carotid sinus pressure-induced bradycardia was associated with increased left ventricular outflow tract obstruction. The carotid sinus pressure-induced increase in the murmur is probably multifactorial: decreased aortic pressure and impedance; increased contractility immediately on sudden slowing of heart rate; further increase in obstruction as the mitral valve systolic anterior movement is enhanced; and delayed vasodilatation maintaining the obstruction even after return of heart rate to precarotid sinus pressure values. An increase in a systolic murmur with carotid sinus pressure is characteristic of HOCM.

Prevalence of systolic anterior motion of the mural (posterior) leaflet of the mitral valve in hypertrophic cardiomyopathy: an echocardiographic study

Cross-sectional echocardiography was used to identify systolic anterior motion of the mural (posterior) leaflet of the mitral valve from a group of 53 patients with hypertrophic cardiomyopathy. This type of systolic anterior motion was identified in parasternal long axis, apical four-chamber and/or long-axis cross-sections and was characterized by an elongation of the mural leaflet and an abnormal coaptation with the aortic (anterior) leaflet. At end-diastole, the aortic leaflet coapted at the basal or mid portion of the mural leaflet, leaving its distal "residual" segment in the left ventricle. Subsequently, during systole this "residual" segment approached or touched the ventricular septum. Systolic anterior motion of the mural leaflet was present in 6 (12%) of our patients with hypertrophic cardiomyopathy. Lengthening of the leaflet and an abnormal coaptation were associated with increased thickening of the posterior wall of the left ventricle and narrowing of the left ventricular outflow tract. All these elements contribute to the occurrence of systolic anterior motion and left ventricular tract obstruction.

Hypertrophic cardiomyopathy: current views on etiology, pathophysiology, and management

Hypertrophic cardiomyopathy (HCM) is a primary myocardial disease of unknown cause that is characterized by a hypertrophied, nondilated, hypercontractile left ventricle. Its etiology and pathogenesis remain undefined but the three principal factors implicated are a genetic predisposition, a hypersensitivity to catecholamines, and an abnormal calcium metabolism. The hypertrophy typically involves the intraventricular septum to varying degrees, but may also involve the apex or free wall and even be concentric. The disease occurs in either an obstructive or a nonobstructive form depending on whether an intraventricular pressure gradient can be demonstrated at rest or on provocation. The gradient and obstruction to outflow is usually seen in patients with asymmetric septal hypertrophy (ASH) and anterior motion of the mitral valve during systole (SAM). Abnormal left ventricular diastolic function characterized by inadequate filling and impaired relaxation has been shown to be very important in both the obstructive and nonobstructive forms of the disease. In addition, inadequate coronary vasodilator reserve as a result of small vessel disease, microvascular spasm, and/or low capillary density per unit myocardial mass has been implicated as an important cause of ischemia in patients without coronary artery disease. HCM is a disease of young adulthood with relatively slow progression; young patients are often asymptomatic, whereas older patients are more limited by dyspnea, angina, dizziness, or syncope. Supraventricular tachyarrhythmias occur in 30% of patients, and high-grade ventricular arrhythmias occur in over 75%. The annual mortality is 3-5%. The common mode of demise is sudden cardiac death. Therefore, the primary objectives of treatment are the amelioration of symptoms, the control of arrhythmias, and the prevention of sudden death. Beta-adrenoreceptor blocking agents decrease myocardial contractility and oxygen demands and increase ventricular volume; therefore, they are most useful in patients with the obstructive form of HCM. Calcium channel antagonists enhance left ventricular relaxation, relieve microvascular spasm, and improve coronary filling and therefore are the agents of choice in patients with diastolic dysfunction. The ability of the calcium channel antagonists to decrease contractility makes them valuable in patients with obstructive HCM. Arterial vasodilators, diuretics, nitrates, and inotropic agents should be avoided because they can increase the intraventricular gradient. Myomyectomy is reserved for those patients with the obstructive form of HCM whose symptoms are refractory to medical therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Intraoperative Doppler echocardiography in hypertrophic cardiomyopathy: correlations with the obstructive gradient

Although significant pressure gradients can be recorded across the left ventricular outflow tract in patients with hypertrophic cardiomyopathy, controversy exists regarding the presence or absence of true obstruction. Ten patients with hypertrophic cardiomyopathy were studied at the time of septal myectomy. A sterile continuous wave Doppler transducer was placed on the ascending aorta and directed toward the left ventricular outflow tract to measure velocity simultaneously with invasive gradient measured using solid-state hub transducers by direct puncture of the left ventricle and aorta. Simultaneous Doppler velocity and invasive gradient measurements (n = 33) were made at rest, before and after myectomy and during interventions with isoproterenol, volume loading and phenylephrine. High velocity flow with a characteristic contour was recorded in patients with a significant gradient. Using the modified Bernoulli equation (gradient = 4 X velocity), a good correlation was found between the Doppler-derived gradient and the peak instantaneous gradient measured invasively (r = 0.93, y = 0.89X + 12, p = 0.0001). Changes in gradient and velocity due to interventions also correlated well (r = 0.96, y = 0.91X - 3, p = 0.0001). Continuous wave Doppler echocardiography can accurately estimate the outflow tract gradient. The magnitude, timing and contour of these high velocity flow signals support the hypothesis that true obstruction is present in patients with hypertrophic cardiomyopathy who have a significant gradient.

Differences in coronary flow and myocardial metabolism at rest and during pacing between patients with obstructive and patients with nonobstructive hypertrophic cardiomyopathy

Fifty patients with hypertrophic cardiomyopathy underwent invasive study of coronary and myocardial hemodynamics in the basal state and during the stress of pacing. The 23 patients with basal obstruction (average left ventricular outflow gradient, 77 +/- 33 mm Hg; left ventricular systolic pressure, 196 +/- 33 mm Hg, mean +/- 1 SD) had significantly lower coronary resistance (0.85 +/- 0.18 versus 1.32 +/- 0.44 mm Hg X min/ml, p less than 0.001) and higher basal coronary flow (106 +/- 20 versus 80 +/- 25 ml/min, p less than 0.001) in the anterior left ventricle, associated with higher regional myocardial oxygen consumption (12.4 +/- 3.6 versus 8.9 +/- 3.3 ml oxygen/min, p less than 0.001) compared with the 27 patients without obstruction (mean left ventricular systolic pressure 134 +/- 18 mm Hg, p less than 0.001). Myocardial oxygen consumption and coronary blood flow were also significantly higher at paced heart rates of 100 and 130 beats/min (the anginal threshold for 41 of the 50 patients) in patients with obstruction compared with those without. In patients with obstruction, transmural coronary flow reserve was exhausted at a heart rate of 130 beats/min; higher heart rates resulted in more severe metabolic evidence of ischemia with all patients experiencing chest pain, associated with an actual increase in coronary resistance. Patients without obstruction also demonstrated evidence of ischemia at heart rates of 130 and 150 beats/min, with 25 of 27 patients experiencing chest pain. In this group, myocardial ischemia occurred at significantly lower coronary flow, higher coronary resistance and lower myocardial oxygen consumption, suggesting more severely impaired flow delivery in this group compared with those with obstruction. Abnormalities in myocardial oxygen extraction and marked elevation in filling pressures during stress were noted in both groups. Thus, obstruction to left ventricular outflow is associated with high left ventricular systolic pressure and oxygen consumption and therefore has important pathogenetic importance to the precipitation of ischemia in patients with hypertrophic cardiomyopathy. Patients without obstruction may have greater impairment in coronary flow delivery during stress.

Left ventricular systolic and diastolic flow abnormalities determined by Doppler echocardiography in obstructive hypertrophic cardiomyopathy

To analyze the relation of systolic anterior motion (SAM) of the mitral valve, peak left ventricular (LV) outflow tract velocity, aortic flow and mitral flow, 17 patients with obstructive hypertrophic cardiomyopathy (HC) (8 men, 9 women), aged 19 to 88 years (mean 45), were studied using M-mode and 2-dimensional echocardiography and pulsed and continuous-wave Doppler echocardiography and results were compared with those from 18 age-matched normal subjects. SAM was present in all patients with HC and absent in normal subjects. Time to peak outflow velocity as a percentage of LV ejection time was 63% in patients with HC and 29% in normal subjects (p less than 0.001). In 13 patients, time from the R-wave peak to the closest approximation of the mitral valve to the ventricular septum or initial contact during SAM was determined and was 242 +/- 66 ms and time from the R-wave peak to the peak LV outflow tract velocity was 242 +/- 73 ms (r = 0.90). In 11 patients time from the R-wave peak to cessation of flow in the ascending aorta was measured and was 286 +/- 80 ms; time from the R-wave peak to the peak LV outflow tract velocity was 246 +/- 75 ms. The ratio of early to late diastolic filling velocities of the left ventricle was 1.47 +/- 0.40 in the normal subjects and 1.26 +/- 0.84 in patients with HC (difference not significant). The early to late ratio of the 12 patients without mitral regurgitation was 0.99 +/- 0.52 (p less than 0.01 vs normal subjects).(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular ejection dynamics in hypertrophic cardiomyopathy and aortic stenosis: comparison with the use of Doppler echocardiography

Left ventricular ejection dynamics of 15 patients with hypertrophic cardiomyopathy (nine obstructive, six nonobstructive) were compared to those in 12 age-matched normal subjects and 10 patients with valvular aortic stenosis by means of combined two-dimensional and Doppler echocardiography. Doppler peak flow velocities in obstructive (HOCM, 2.5 +/- 1.3 m/sec) and nonobstructive (HNCM, 2.6 +/- 0.6 m/sec) hypertrophic cardiomyopathy, as well as in patients with aortic stenosis (AS, 3.6 +/- 1.3 m/sec) were significantly higher than in the normal population (1.0 +/- 0.2 m/sec; p less than 0.001 for all comparisons), but did not differ from each other. The HOCM patients had time to peak velocity (154 +/- 55.7 msec) that was higher than that in both HNCM (86 +/- 8.4 msec) and normal groups (84.5 +/- 8.9 msec; p less than 0.001 for both comparisons), but did not differ from those in AS (117 +/- 52.5 msec). The total ejection time did not differ between HOCM (348.2 +/- 91.1 msec) and AS (328.8 +/- 30.4 msec) groups, but was prolonged in HOCM compared to HNCM (198 +/- 21.0 msec) and normal groups (233 +/- 28.3 msec; p less than 0.001 for both comparisons). The normal and HNCM groups did not differ in time to peak or total ejection time measurements. The percent of flow velocity present in the initial third of the systolic velocity integral for HOCM (44.5% +/- 5.9) and HNCM (49.4% +/- 2.5) groups was greater than for normals (36.2% +/- 5.4; p less than 0.05 for both comparisons), but HOCM values did not differ from HNCM values.(ABSTRACT TRUNCATED AT 250 WORDS)