Detection of regional left ventricular asynchrony in obstructive hypertrophic cardiomyopathy by magnetic resonance imaging

Heterogeneity of apex-to-base dispersion in diastolic lengthening is related to impaired global left ventricular relaxation in patients with hypertrophic cardiomyopathy

BACKGROUND

The presence of apex-to-base disparity in diastolic left ventricle (LV) endocardial lengthening, based on an electromechanical activation sequence, has been recognized as an important determinant of LV diastolic properties. However, the behavior of LV apical and basal diastolic lengthening and its relationship to LV filling in hypertrophic cardiomyopathy (HCM) are unknown.

METHODS

We obtained basal and apical LV short-axis views in 27 patients with non-obstructive HCM and 25 healthy volunteers. The patients with HCM were subdivided into two groups; those with apical hypertrophy [APH(+)] or those without apical hypertrophy [APH(-)]. Eight equiangular points on the endo-myocardium at end diastole were placed in each view, and the movements of these points were automatically tracked using a two-dimensional echocardiographic tissue tracking system. Time-LV internal diameter curves were obtained and averaged. The time intervals from the aortic valve closure to the point of the first 40% of peak diastolic lengthening (T 40) were measured in each view. The standard deviation of the time to peak systolic circumferential shortening at the base and apex were calculated to assess the heterogeneity of LV contraction.

RESULTS

The time difference in the T 40 between the apex and base (dt-T 40) in the HCM-APH(+) and HCM-APH(-) groups was greater than that in the control group. The heterogeneities in LV apical systolic shortening in the HCM groups were greater than those in the control group. There were good linear correlations between the dt-T 40 and the LV early diastolic echo-parameters and the LV mass index.

CONCLUSIONS

Delayed apical relaxation and filling in patients with HCM is related to LV diastolic dysfunction and systolic dyssynchronous contraction.

Hypertrophic Cardiomyopathy Is Associated with More Severe Left Ventricular Dyssynchrony than Is Hypertensive Left Ventricular Hypertrophy

OBJECTIVE

To evaluate left ventricular (LV) dyssynchrony in patients with left ventricular hypertrophy (LVH), and to compare abnormalities associated with hypertrophic cardiomyopathy (HCM) and hypertensive heart disease (HHD) using 2D speckle tracking imaging.

METHODS

Basal, middle, and apical 2D LV short-axis images were acquired in 43 patients with LVH including 20 with HCM and 23 with HHD, and in 15 age-matched controls. Radial strain, circumferential strain, time interval from the R-wave to peak radial strain (Trs), and time to peak circumferential strain (Tcs) were measured in six equidistant segments at each level of the 3 LV short-axis views using 2D speckle tracking analysis. To assess LV dyssynchrony, Trs(cs)-18SD, the standard deviation (SD) of Trs(cs) in all 18 segments, was calculated.

RESULTS

Regional radial strain in the middle and apical short-axis segments was significantly less in patients with HCM than in those with HHD. Regional circumferential strain in the apical short-axis segments was also less in HCM. Trs-18SD and Tcs-18SD were significantly longer in patients with HCM than in age-matched controls and patients with HHD (Trs-18SD: HCM: 88 +/- 32 ms, HHD: 51 +/- 20 ms, control: 45 +/- 12 ms P < 0.001, Tcs-18SD: HCM: 71 +/- 27 ms, HHD: 46 +/- 14 ms, control: 45 +/- 14 ms P < 0.001).

CONCLUSIONS

The presence of LVH is thus not always associated with LV dyssynchrony. However, the greater reduction of regional strain and severe LV dyssynchrony in HCM may contribute to the adverse cardiovascular outcomes associated with this disease.

Noninvasive cardiac imaging in patients with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy and the most common cause of cardiac death in young athletes in the U.S. Noninvasive imaging plays an important role in detecting the disease, understanding its pathophysiology, and selecting as well as guiding appropriate therapy. In this review, we discuss the existing methodology with emphasis on current and emerging clinical applications in patients with HCM.

Effects of carvedilol on left ventricular remodelling in chronic stable heart failure: a cardiovascular magnetic resonance study

BACKGROUND

The ability of beta blockers to improve left ventricular function has been demonstrated, but data on the effects on cardiac remodelling are limited.

OBJECTIVE

To investigate, using cardiovascular magnetic resonance (CMR), the effects of carvedilol on left ventricular remodelling in patients with chronic stable heart failure and left ventricular systolic dysfunction caused by coronary artery disease.

DESIGN

Randomised, double blind, placebo controlled study.

SETTING

Chronic stable heart failure.

PATIENTS AND INTERVENTION

34 patients with chronic stable heart failure and left ventricular systolic function taking part in the CHRISTMAS trial (double blind carvedilol v placebo) underwent CMR before randomisation and after six months of treatment.

MAIN OUTCOME MEASURE

Left ventricular remodelling at six months.

RESULTS

The carvedilol and placebo groups were well balanced at baseline, with no significant intergroup differences. Over the study period, there was a significant reduction in end systolic volume index (ESV(I)) and end diastolic volume index (EDV(I)) between the carvedilol and the placebo group (carvedilol -9 v placebo +3 ml/m2, p = 0.0004; carvedilol -8 v placebo 0 ml/m2, p = 0.05). The ejection fraction increased significantly between the groups (carvedilol +3% v placebo -2%, p = 0.003).

CONCLUSIONS

Treatment of chronic stable heart failure with carvedilol results in significant improvement in left ventricular volumes and function. These effects might contribute to the benefits of carvedilol on mortality and morbidity in patients with chronic heart failure.

Noninvasive modalities. Cardiac MR imaging

As outlined in this article, the strength of MR imaging is that it can provide flow, function, and in some cases metabolic data in a single examination, independent of patient body habitus. Future prospects for real-time imaging and in vivo mapping of fiber orientation promise further advances in our understanding of the structure-function relationship in diastole. Many of the MR imaging methods that have been developed for cardiovascular imaging are now mature and available on state-of-the-art scanners. Although MR imaging can provide detailed characterization of diastolic function, there is a paucity of clinical results which could lead to use guidelines. When more clinicians have access and become familiar with MR imaging, and the type of information that it can provide, clinical trials will be needed to establish the role of MR imaging for evaluation of diastolic function. In the meantime, MR imaging remains an excellent research tool for this application and will help yield further insights into the pathophysiology of diastolic dysfunction.

Assessment of the Systolic Left Ventricular Myocardial Velocity Profile and Gradient Using Tissue Doppler Imaging in Patients with Hypertrophic Cardiomyopathy

To determine the systolic characteristics of the hypertrophied myocardium in patients with hypertrophic cardiomyopathy (HCM), we evaluated the left ventricular [left ventricle (LV)] myocardial velocity profile (MVP) and gradient obtained from tissue Doppler imaging (TDI). Transmural wall-motion velocities in the ventricular septum and LV posterior wall were recorded in 12 patients with asymmetric septal hypertrophy and 12 healthy volunteers, and their profiles and gradients were determined. The maximum systolic myocardial velocity gradient in the ventricular septum was significantly lower in the HCM group than in the control group (0.88 +/- 0.35 versus 2.24 +/- 0.41; P < 0.001), whereas the gradient in the LV posterior wall was only slightly lower in the HCM group than in the control group (2.69 +/- 0.82 versus 3.45 +/- 0.96). In the control group, the MVPs in the ventricular septum and LV posterior wall were closely linear, suggesting that the transmural velocity is uniform during systole. MVPs in the ventricular septum and LV posterior wall in the HCM group also were closely linear, whereas the distribution of velocities in the ventricular septum was fairly dispersed compared with the control group. The myocardial velocity gradient on the right ventricular side of the ventricular septum decreased or disappeared in the patients with HCM, suggesting a nonuniform distribution of velocities. In conclusion, the MVP and gradient obtained from TDI may represent new indices for evaluating regional LV contractile abnormality in patients with HCM.

Regional left ventricular myocardial contraction abnormalities and asynchrony in patients with hypertrophic cardiomyopathy evaluated by magnetic resonance spatial modulation of magnetization myocardial tagging

Global left ventricular (LV) pump function is generally preserved in patients with hypertrophic cardiomyopathy (HCM). However, it is unknown whether regional myocardial contractility is impaired, especially in nonhypertrophied regions. The purpose of this study was to evaluate regional LV myocardial contraction in patients with HCM using magnetic resonance (MR) spatial modulation of magnetization (SPAMM) myocardial tagging. The study group comprised 20 patients with asymmetric septal hypertrophy (HCM group) and 16 age-matched normal patients (control group), and data were collected using transthoracic M-mode and 2-dimensional echocardiography, and MR SPAMM myocardial tagging. The systolic strain ratio, maximum systolic strain velocity, and time from end-diastole to maximum systolic strain (deltaT) in the anterior, ventricular septal, inferior and lateral regions for 2 LV short-axis sections at the levels of the chordae tendineae and papillary muscles were measured at 50-ms intervals by MR myocardial tagging. The end-diastolic anterior and ventricular septal wall thicknesses and LV mass index were significantly different between the HCM and control groups. The systolic strain ratio for all 4 walls, particularly the anterior and ventricular septal regions, was significantly lower in the HCM group. In the HCM group, the maximum systolic strain velocity was significantly lower and deltaT was significantly shorter for all 4 walls, particularly the anterior and ventricular septal regions. The standard deviation for the deltaT, calculated from the deltaT for the 8 regions of the 2 LV short-axis sections, was significantly greater in the HCM group. In conclusion, regional LV myocardial contraction is impaired in both hypertrophied and nonhypertrophied regions, and systolic LV wall asynchrony occurs in patients with HCM.

Determination of normal regional left ventricular function from cine-MR images using a semi-automated edge detection method

A semi-automated edge detection method for the delineation of the endo- and epicardial borders of the left ventricle from cine MR images has been developed. The feasibility of this was demonstrated by processing end diastolic and end systolic ECG-gated images of four short axis images in 10 healthy subjects. The first derivative method combined with a 2D weighted polynomial fitting procedure was used to determine the endo- and epicardial borders, which then allowed determination of the wall motion, wall thickening, and ejection fraction, of the left ventricle. The results show that the end-systolic radial wall motion varies from (32+/-8)% to (76+/-12)%, and wall thickening from (0.60+/-0.46) cm to (1.26+/-0.50) cm. An average ejection fraction of (69+/-6)% was found which agrees well with literature values. The method described, for the delineation of the borders, reduces considerably the long and tedious operator time inherent in manual measurement and greatly increases the reproducibility of the measurements.

New diagnostic options in hypertrophic cardiomyopathy

The pathophysiologic features and clinical manifestations of HCM have been elucidated by the introduction of several new diagnostic options. Knowledge of the molecular defects of HCM has advanced rapidly, and genetic screening studies have reemphasized the value of the standard electrocardiogram as an initial screening tool. Analysis of heart rate variability, late potentials, and QT dispersion were not found to be reliable prognostic markers in HCM. However, measurement of dispersion of conduction is probably a sensitive technique in identifying a high risk for sudden cardiac death. Significant developments include transthoracic and transesophageal echocardiography and their role in studying the mitral valve, early detection of left ventricular chamber dilatation, analysis of coronary flow, and intraoperative echocardiography. Finally, advances in the application of magnetic resonance imaging and positron-emission tomography are underway.

Long-term results of left ventricular myotomy and myectomy for obstructive hypertrophic cardiomyopathy

A retrospective analysis of patients with hypertrophic obstructive cardiomyopathy treated by left ventricular myotomy and myectomy from 1972 to 1994 is reported. There were 158 patients (81 male and 77 female) with a mean age of 50.2(+/-17.2) years (range 12 to 80 years). One hundred nine patients (69%) were 60 years of age or younger, and 49 patients (31%) were older than 60 years. The overall mean follow-up period was 6.1(+/-4.8) years (range 0.1 to 19.3 years) and was 94% complete with a cumulative total of 956 patient-years. Preoperative exertional dyspnea was present in 84%, chest pain in 70%, presyncope in 54%, syncope in 31%, and cardiac arrest in 5% of patients. Preoperative cardiac catheterization was done in 150 patients, with mitral regurgitation detected in 104 patients (67%). The average maximal provocable left ventricular outflow tract gradient was 118 (+/-46) mm Hg (range 25 to 250 mm Hg). The average preoperative echocardiographic gradient at rest was 64 mm Hg, 20 mm Hg in the early postoperative period and 10 mm Hg in the late postoperative period. The mean septal thickness was 2.2 (+/-0.6) cm, 1.9 (+/-0.7) cm in the early postoperative period (p < 0.05 vs preoperative) and 1.7 (+/- 0.5) cm in the late postoperative period (p < 0.05 vs preoperative). The overall 30-day operative mortality rate was 3.2% (5/158), and 0% for 109 patients 60 years of age or younger. Causes of death included myocardial infarction and left ventricular free wall rupture, myocardial failure from septal perforation, sepsis, cerebrovascular accident caused by thromboembolism, and delayed cardiac tamponade in one patient each. Concomitant coronary artery bypass grafting was performed in 22 patients (19.3% of patients > or = to 40 years of age) and mitral valve replacement in 5 patients (3.2%). One hundred nine patients (69%) are alive, 10 patients (6.3%) were lost to follow-up, and 39 patients died (24.7%), including operative deaths). Actuarial survivals at 1, 5, 10, and 15 years were 92.4% +/- 2.2%, 85.4% +/- 3.1%, 71.5 +/- 4.6%, and 46% +/- 9%, respectively. The overall linearized death rate for discharged patients was 1.9%/pt-yr, and for cardiac related deaths it was 1.7%/pt-yr. Thirty-nine (36%) of the 109 survivors received beta-adrenergic blockers, and 30 (28%) received calcium channel blockers. Ninety-four patients had improvement in New York Heart Association functional class, 10 had improvement in symptoms but not in functional class, and 5 had no improvement in functional class or symptoms. Neither preoperative hemodynamic values nor routine echocardiographic measurements significantly correlated with quality of postoperative results. Left ventricular myotomy and myectomy is a safe and reproducibly effective operative treatment for medically refractory hypertrophic obstructive cardiomyopathy, especially for patients 60 years of age or younger. Improvement in functional class and symptoms can be expected in nearly all patients 60 years of age or younger. Improvement in functional class and symptoms can be expected in nearly all patients. The results of myotomy and myectomy serve as a standard for comparison with other interventions for medically refractory cardiomyopathy.

MR imaging of regional cardiac function: low-pass filtering of wall thickness curves

Wall thickness curves (WTCs) derived from MR images are subject to considerable measurement error. This study determines the effects of low-pass Fourier filtering of WTCs on functional parameters derived from the curve: peak rate of wall thinning (PRWT) and time to PRWT (TPRWT). The inter-subject standard deviation (SD) of PRWT changed from 0.35 to 0.18, and the SD of TPRWT from 34.3 to 29.5. Differences between neighboring segments decreased from 0.31 to 0.15% mean thickness/ms for PRWT (P = 0.012), and from 35.0 to 19.0 ms for TPRWT (P = 0.005). It is concluded that filtering of MR imaging-derived WTCs contributes to a better representation of myocardial wall motion.