Evaluation of hypertrophic cardiomyopathy by Doppler color flow imaging: initial observations

Exaggerated myocardial torsion may contribute to dynamic left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

Aims

Dynamic left ventricular (LV) outflow tract obstruction (LVOTO) is associated with symptoms and increased risk of developing heart failure in hypertrophic cardiomyopathy (HCM). The association of LVOTO and LV twist mechanics has not been well studied in HCM. The aim of the study was to compare the pattern of LV twist in patients with HCM associated with asymmetrical septal hypertrophy with and without LVOTO.

Methods and results

Echocardiography (including speckle tracking) was performed in 212 patients with HCM, divided according to the absence (n = 130) or presence (n = 82) of LVOTO (defined as peak pressure gradient ≥30 mmHg either at rest and/or with Valsalva manoeuvre). Patients with LVOTO were older, had smaller LV dimensions, a higher LV ejection fraction (LVEF), a longer anterior mitral valve leaflet length, and a higher early transmitral pulsed wave to septal tissue Doppler velocity ratio (E/E'). A univariate analysis showed that peak twist was significantly higher in patients with LVOTO compared with patients without LVOTO (19.7 ± 7.3 vs. 15.7 ± 6.0, P = 0.00015). Peak twist was similarly enhanced in patients with LVOTO, manifesting only during Valsalva (19.2 ± 5.6, P = 0.007) and patients with resting LVOTO (19.9 ± 8.0, P = 0.00004) compared with patients without LVOTO (15.7 ± 6.0). A stepwise forward logistic regression analysis showed that LVEF, LV end-systolic dimension indexed to body surface area, anterior mitral valve leaflet length, E/E', and peak twist were all independently associated with LVOTO.

Conclusion

This study demonstrates that increased peak LV twist is independently associated with LVOTO in patients with HCM. Peak twist was similarly exaggerated in patients with only latent LVOTO, suggesting that it may play a contributory role to LVOTO in HCM.

Hypertrophic Obstructive Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is caused by mutations in a number of genes. Its prevalence is 0.2% to 0.6%.

METHODS

This review is based on publications retrieved by a selective literature search and on the authors' clinical experi- ence.

RESULTS

70% of patients with HCM suffer from the obstructive type of the condition, clinically characterized by highly dynamic and variable manifestations in the form of dyspnea, angina pectoris, and stress-dependent presyncope and syn- cope. Younger patients are at particular risk of sudden cardiac death; thus, all patients need not only symptomatic treatment, but also risk assessment, which can be difficult in individual cases. Left ventricular obstruction, which usually causes symptoms, is treated medically at first, with either a beta- blocker or verapamil. If medical treatment fails, two invasive treatments are available, surgical myectomy and percu- taneous septum ablation. Both of these require a high level of expertise. If performed successfully, they lead to sustained gradient reduction and clinical improvement. Septum ablation is associated with low perioperative and peri-interventional mortality but necessitates permanent pacemaker implantation in 10-20% of patients.

CONCLUSION

In the absence of evidence from randomized comparison trials, a suitable method of reducing the gradient should be determined by an HCM team in conjunction with each individual patient. Important criteria for decision-making include the anatomical findings and any accompanying illnesses.

Hypertrophic Obstructive Cardiomyopathy: Surgical Myectomy and Septal Ablation

Hypertrophic cardiomyopathy is a genetic disorder characterized by marked hypertrophy of the myocardium. It is frequently accompanied by dynamic left ventricular outflow tract obstruction and symptoms of dyspnea, angina, and syncope. The initial therapy for symptomatic patients with obstruction is medical therapy with β-blockers and calcium antagonists. However, there remain a subset of patients who have continued severe symptoms, which are unresponsive to medical therapy. These patients can be treated with septal reduction therapy, either surgical septal myectomy or alcohol septal ablation. When performed by experienced operators working in high-volume centers, septal myectomy is highly effective with a >90% relief of obstruction and improvement in symptoms. The perioperative mortality rate for isolated septal myectomy in most centers is <1%. Alcohol septal ablation is a less invasive treatment. In many patients, the hemodynamic and clinical results are comparable to that of septal myectomy. However, the results of alcohol septal ablation are dependent on the septal perforator artery supplying the area of the contact between the hypertrophied septum and the anterior leaflet of the mitral valve. There are some patients, particularly younger patients with severe hypertrophy, who do not uniformly experience complete relief of obstruction and symptoms. Both techniques of septal reduction therapy are highly operator dependent. The final decision as to which approach should be selected in any given patient is dependent up patient preference and the availability and experience of the operator and institution at which the patient is being treated.

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.

Pediatric myocardial disease

Cardiomyopathies are diseases of the heart muscles. This article reviews the causes, clinical presentation, diagnosis, management, and long-term outcomes of dilated and hypertrophic cardiomyopathy.

Dual-chamber pacing for hypertrophic cardiomyopathy: a randomized, double-blind, crossover trial

OBJECTIVES

In a double-blind, randomized, crossover trial we sought to evaluate the effect of dual-chamber pacing in patients with severe symptoms of hypertrophic obstructive cardiomyopathy.

BACKGROUND

Recently, several cohort trials showed that implantation of a dual-chamber pacemaker in patients with severely symptomatic hypertrophic obstructive cardiomyopathy can relieve symptoms and decrease the severity of the left ventricular outflow tract gradient. However, the outcome of dual-chamber pacing has not been compared with that of standard therapy in a randomized, double-blind trial.

METHODS

Twenty-one patients with severely symptomatic hypertrophic obstructive cardiomyopathy were entered into this trial after baseline studies consisting of Minnesota quality-of-life assessment, two-dimensional and Doppler echocardiography and cardiopulmonary exercise tests. Nineteen patients completed the protocol and underwent double-blind randomization to either DDD pacing for 3 months followed by backup AAI pacing for 3 months, or the same study arms in reverse order.

RESULTS

Left ventricular outflow tract gradient decreased significantly to 55 +/- 38 mm Hg after DDD pacing compared with the baseline gradient of 76 +/- 61 mm Hg (p < 0.05) and the gradient of 83 +/- 59 mm Hg after AAI pacing (p < 0.05). Quality-of-life score and exercise duration were significantly improved from the baseline state after the DDD arm but were not significantly different between the DDD arm and the backup AAI arm. Peak oxygen consumption did not significantly differ among the three periods. Overall, 63% of patients had symptomatic improvement during the DDD arm, but 42% also had symptomatic improvement during the AAI backup arm. In addition, 31% had no change and 5% had deterioration of symptoms during the DDD pacing arm.

CONCLUSIONS

Dual-chamber pacing may relieve symptoms and decrease gradient in patients with hypertrophic obstructive cardiomyopathy. In some patients, however, symptoms do not change or even become worse with dual-chamber pacing. Subjective symptomatic improvement can also occur from implantation of the pacemaker without its hemodynamic benefit, suggesting the role of a placebo effect. Long-term follow-up of a large number of patients in randomized trials is necessary before dual-chamber pacing can be recommended for all patients with severely symptomatic hypertrophic obstructive cardiomyopathy.

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.

Extent of clinical improvement after surgical treatment of hypertrophic obstructive cardiomyopathy

BACKGROUND

A subgroup of patients with hypertrophic obstructive cardiomyopathy remain severely symptomatic despite optimal medical therapy. Septal myectomy reduces or eliminates left ventricular outflow obstruction and produces marked symptomatic improvement. With the recent advent of alternative methods for treatment of this disorder, such as dual-chamber pacing, it is necessary to establish the risks and benefits of septal myectomy in the modern surgical era.

METHODS AND RESULTS

The clinical, ECG, echocardiographic, cardiac catheterization, and surgical data were analyzed for 65 patients 20 to 70 years old with hypertrophic obstructive cardiomyopathy who had surgical treatment between 1986 and 1992. Specific symptoms and overall functional status were evaluated before surgery and at the end of the first postoperative year. Subsequent long-term clinical postoperative follow-up was also obtained. The extent of postoperative improvement was measured by the presence and severity of persistent symptoms, overall New York Heart Association (NYHA) functional class, and patients' self-perceptions of overall improvement. Of the patients, 95% were in NYHA functional class III or IV before surgery: 95% had dyspnea, 62% had angina, 63% had near-syncope, and 23% had syncope. The overall early mortality rate was 4.6%; there was no mortality among the 45 patients who underwent isolated septal myectomy. At the 1-year postoperative evaluation, 89% of survivors were in NYHA functional class I or II, and 47% believed that they had 100% improvement. Significant improvement (as defined) was seen in 67% of patients with dyspnea, 90% with angina, 86% with near-syncope, and 100% with syncope. The 5-year survival rate was 92%.

CONCLUSIONS

The results of the present study reaffirm the efficacy of surgical treatment of hypertrophic obstructive cardiomyopathy in patients who are severely symptomatic despite optimal medical therapy and serve as a useful reference by which the surgical approach can be compared with new and potentially promising treatment alternatives.

Transesophageal echocardiographic evaluation of mitral regurgitation in hypertrophic cardiomyopathy: contributions of eccentric left ventricular hypertrophy and related abnormalities of the mitral complex

This study was designed to evaluate the contribution of eccentric left ventricular hypertrophy and its related organic and spatial abnormalities of the mitral complex to the occurrence of mitral regurgitation in patients with hypertrophic cardiomyopathy We selected 45 consecutive patients with systolic mitral regurgitation by color Doppler echocardiography and performed transesophageal echocardiography in all patients. Eighteen patients were in the obstructive group and 27 patients were in the nonobstructive group of hypertrophic cardiomyopathy with asymmetric septal hypertrophy. Twenty subjects without any cardiac disorders served as the control group. The maximum area of mitral regurgitation was significantly greater in the obstructive group than in the nonobstructive group. Mitral regurgitation appeared more frequently during pansystole in the two groups with hypertrophic cardiomyopathy, particularly in the obstructive group. Mitral valve prolapse was observed in 20 (44%) of the 45 patients with hypertrophic cardiomyopathy. Distances between the posterior papillary muscle and anterior or posterior mitral anulus were significantly smaller in the two groups with hypertrophic cardiomyopathy than in the normal control group. In the obstructive group, the length of the anterior mitral leaflet and the thickness of the rough zone of the anterior mitral leaflet at mid-diastole were significantly greater than in the other groups. Systolic anterior motion was observed in all patients with obstructive cardiomyopathy and contact between the interventricular septum and the anterior mitral leaflet during early diastole was observed in 17 of the 18 patients in the obstructive group.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative hemodynamics by Doppler echocardiography: a noninvasive alternative to cardiac catheterization

Doppler echocardiography has greatly enhanced the information provided by two-dimensional echocardiography. By providing information concerning pressure gradients, intracardiac pressures, volumetric flow, and diastolic filling of the heart, most hemodynamic information that in the past could be obtained only from cardiac catheterization can now be provided accurately and noninvasively by Doppler echocardiography. Future developments in instrument technology and understanding of the various Doppler velocity curves should further aid in the ability to obtain a complete, noninvasive hemodynamic assessment of the patient with cardiac disease.

Intraoperative echocardiography for surgical repair of the aortic valve and left ventricular outflow tract

Valve conservation surgery represents an exciting advance in the evolution of valve surgery. Recent studies have shown the significant advantages of mitral valve repair over valve replacement. While there are significant advantages for valve repair, the surgeon requires a greater understanding of the mechanism of valvular dysfunction prior to repair and requires an accurate means to assess the adequacy of the repair in the operating room immediately following the repair. Intraoperative echocardiography with color flow Doppler mapping provides immediate and accurate assessment of cardiac anatomy, hemodynamics, and valve integrity. These data are vital for optimal intraoperative surgical decision making. Intraoperative echocardiography has an important role in the evaluation in patients undergoing surgery to the aortic valve and left ventricular outflow tract by the delineation of presence and mechanism of left ventricular outflow tract obstruction, the quantification of severity of the left ventricular outflow tract gradient, the severity and mechanism of aortic regurgitation, the distribution and severity of left ventricular hypertrophy, and identification of associated lesions such as mitral regurgitation. Aortic valve conservation surgery is more complex than mitral valve surgery. The surgical techniques for aortic valve repair have been slower to evolve than mitral repair with a much smaller percentage of patients currently suitable for valve repair. However, with the aid of intraoperative echocardiography, the future shows similar promise that has already been fulfilled with mitral valve repair. Even in its infancy, intraoperative echocardiography has become indispensable to the innovative cardiac surgeon. However, without consideration of adequate echocardiographic training, incorrect echocardiography diagnoses can lead to inappropriate surgical decisions.

Cardiomyopathy in the young

The application of echocardiography is most helpful in recognizing hypertrophic or congestive cardiomyopathy. It cannot determine the cause of such findings but rather provides the clinician with useful information that may over time allow the correct diagnosis to become clearer. The alterations in hemodynamics after surgical or pharmacologic intervention can easily be evaluated with echo Doppler applications. Herein lies one of the major strengths of echocardiography: frequent sequential evaluation. The role of Doppler color flow imaging is just emerging. As time goes on, it may add useful information not otherwise obtained by the existing technology.

Echocardiographic and Doppler assessment of hypertrophic cardiomyopathy

Echocardiographic and Doppler studies are invaluable in the detection and management of patients with hypertrophic cardiomyopathy, since virtually all aspects of the disorder can be evaluated. Echocardiography is the primary method of diagnosis, and hemodynamic studies are required usually only when surgery is contemplated. All patients should if possible undergo complete M-mode, two-dimensional, Doppler, and color flow studies to define the extent of hypertrophy, the hemodynamic subgroup, quantitation of left ventricular outflow obstruction, mitral regurgitation when present, and an assessment of diastolic function. Patients undergoing medical or surgical therapy for this disorder should have repeat studies performed to assess the effects of therapy on the degree of obstruction and diastolic dysfunction.

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)

Signal processing in 2 dimensional Doppler echocardiography

Blood flow recordings made by 2 dimensional Doppler echocardiography can sometimes be understood more easily than conventional Doppler recordings, because of the anatomical 2 dimensional presentation. In contrast, signal processing has become more complicated and requires more explanation. In 2 dimensional Doppler echocardiography the analog ultrasonic signal received by the transducer is converted into an audible signal, which next is digitized and analyzed for its mean frequency and variance. Data collection and processing require application of multigating and high speed frequency analysis, generally based upon autocorrelation. Some artifacts may be perceived, such as color reversal due to aliasing, deceptively colored tissue surfaces due to beam motion, and wall motion ghost signals due to multiple reflections. Color flow imaging is appropriate for a rapid scan of the heart cavities to detect and roughly evaluate flow abnormalities. Quantification is still accomplished by switching to conventional Doppler mode.