Heterogeneity of ventricular function and myocardial oxidative metabolism in nonischemic dilated cardiomyopathy

Novel indices representing heterogeneous distributions of myocardial perfusion imaging

INTRODUCTION

Heterogeneous distribution in myocardial perfusion images (MPI) obtained by scintigraphy is often observed in cardiac diseases with normal myocardial perfusion. However, quantitative assessments of such heterogeneity have not been established. We hypothesized that the heterogeneity in MPI can be quantitatively evaluated through histogram analysis, calculating the standard deviation (SD), the 95% bandwidth (BW95%), and entropy.

METHODS

We examined resting 99mTc-MIBI images in 20 healthy subjects and 29 patients with cardiac disease who had none or very-mild reduced myocardial perfusion evaluated as a low summed rest score (0 to 4, the range of the studied healthy subjects). Two nuclear medicine specialists blindly divided them into two groups: non-heterogeneity or heterogeneity group, based solely on their visual assessments of heterogeneity on splash and polar maps generated from single-photon emission computed tomography (SPECT) images. The %uptake was determined by dividing the tracer count of each pixel by the tracer count of the pixel with the highest value in the LV myocardium. SD, BW95%, and entropy from histogram patterns were analyzed from the polar map data array of each %uptake. We investigated whether heterogeneity could be assessed using SD, BW95, and entropy in two groups classified by visual assessments. Additionally, we evaluated the area under the curve (AUC) to identify heterogeneity in the receiver operating characteristic curve analysis.

RESULTS

Based solely on visual assessments, 11 (22%) and 38 (78%) cases were classified into the non-heterogeneity and heterogeneity groups, respectively. The non-heterogeneity group consisted of only healthy subjects, and all patients with cardiac disease were classified into the heterogeneity group. The cases in the heterogeneity group had significantly higher values of heterogeneity indices (SD, BW95%, and entropy) in %uptake than those in the non-heterogeneity group (p < 0.05 for all). The AUCs of the heterogeneity indices were sufficiently high (AUCs > 0.90 for all) in distinguishing cases with visually heterogeneous distribution or patients with cardiac disease.

CONCLUSIONS

Heterogeneity in MPI can be evaluated using SD, BW95%, and entropy through histogram analysis. These novel indices may help identify patients with subtle myocardial changes, even in images that show preserved perfusion (345/350).

CARDIOKIN1: Computational Assessment of Myocardial Metabolic Capability in Healthy Controls and Patients With Valve Diseases

Supplemental Digital Content is available in the text.

Background:

Many heart diseases can result in reduced pumping capacity of the heart muscle. A mismatch between ATP demand and ATP production of cardiomyocytes is one of the possible causes. Assessment of the relation between myocardial ATP production (MV_ATP) and cardiac workload is important for better understanding disease development and choice of nutritional or pharmacologic treatment strategies. Because there is no method for measuring MV_ATP in vivo, the use of physiology-based metabolic models in conjunction with protein abundance data is an attractive approach.

METHOD:

We developed a comprehensive kinetic model of cardiac energy metabolism (CARDIOKIN1) that recapitulates numerous experimental findings on cardiac metabolism obtained with isolated cardiomyocytes, perfused animal hearts, and in vivo studies with humans. We used the model to assess the energy status of the left ventricle of healthy participants and patients with aortic stenosis and mitral valve insufficiency. Maximal enzyme activities were individually scaled by means of protein abundances in left ventricle tissue samples. The energy status of the left ventricle was quantified by the ATP consumption at rest (MV_ATP[rest]), at maximal workload (MV_ATP[max]), and by the myocardial ATP production reserve, representing the span between MV_ATP(rest) and MV_ATP(max).

Results:

Compared with controls, in both groups of patients, MV_ATP(rest) was increased and MV_ATP(max) was decreased, resulting in a decreased myocardial ATP production reserve, although all patients had preserved ejection fraction. The variance of the energetic status was high, ranging from decreased to normal values. In both patient groups, the energetic status was tightly associated with mechanic energy demand. A decrease of MV_ATP(max) was associated with a decrease of the cardiac output, indicating that cardiac functionality and energetic performance of the ventricle are closely coupled.

Conclusions:

Our analysis suggests that the ATP-producing capacity of the left ventricle of patients with valvular dysfunction is generally diminished and correlates positively with mechanical energy demand and cardiac output. However, large differences exist in the energetic state of the myocardium even in patients with similar clinical or image-based markers of hypertrophy and pump function.

Registration:

URL: https://www.clinicaltrials.gov; Unique identifiers: NCT03172338 and NCT04068740.

Strain parameters for predicting the prognosis of non-ischemic dilated cardiomyopathy using cardiovascular magnetic resonance tissue feature tracking

BACKGROUND

A considerable number of non-ischemic dilated cardiomyopathy (NDCM) patients had been found to have normalized left ventricular (LV) size and systolic function with tailored medical treatments. Accordingly, we aimed to evaluate if strain parameters assessed by cardiovascular magnetic resonance (CMR) feature tracking (FT) analysis could predict the NDCM recovery.

METHODS

79 newly diagnosed NDCM patients who underwent baseline and follow-up CMR scans were enrolled. Recovery was defined as a current normalized LV size and systolic function evaluated by CMR.

RESULTS

Among 79 patients, 21 (27%) were confirmed recovered at a median follow-up of 36 months. Recovered patients presented with faster heart rates (HR) and larger body surface area (BSA) at baseline (P < 0.05). Compared to unrecovered patients, recovered pateints had a higher LV apical radial strain divided by basal radial strain (RSapi/bas) and a lower standard deviation of time to peak radial strain in 16 segments of the LV (SD16-TTPRS). According to a multivariate logistic regression model, RSapi/bas (P = 0.035) and SD16-TTPRS (P = 0.012) resulted as significant predictors for differentiation of recovered from unrecovered patients. The sensitivity and specificity of RSapi/bas and SD16-TTPRS for predicting recovered conditions were 76%, 67%, and 91%, 59%, with the area under the curve of 0.75 and 0.76, respectively. Further, Kaplan Meier survival analysis showed that patients with RSapi/bas ≥ 0.95% and SD16-FTPRS ≤ 111 ms had the highest recovery rate (65%, P = 0.027).

CONCLUSIONS

RSapi/bas and CMR SD16-TTPRS may be used as non-invasive parameters for predicting LV recovery in NDCM. This finding may be beneficial for subsequent treatments and prognosis of NDCM patients. Registration number: ChiCTR-POC-17012586.

Dilated Cardiomyopathy: Normalized Multiparametric Myocardial Strain Predicts Contractile Recovery

BACKGROUND

Left ventricular contractile injury in dilated cardiomyopathy (DCM) may occur in a consistently heterogeneous distribution, suggesting that early-injury sentinel regions may have prognostic significance. Heightened surveillance of these regions with high-resolution contractile metrics may predict recovery in DCM.

METHODS

Multiple three-dimensional strain parameters were calculated at each of 15,300 left ventricular grid points from systolic displacement data obtained from cardiac magnetic resonance imaging in 124 test subjects. In 24 DCM patients, Z-scores for two strain parameters at each grid point were calculated by comparison of patient-specific strain values to respective point-specific mean and standard deviation values from a normal human strain database (n = 100). Multiparametric strain Z-scores were averaged over six left ventricular regions at basilar, mid, and apical levels (18 subregions). Patients with DCM were stratified into three groups on the basis of a blinded review of clinical contractile recovery (complete, n = 7; incomplete, n = 7; none, n = 10).

RESULTS

Basilar-septal subregions were consistently heavily injured. Basilar-septal Z-scores were significantly larger (worse) than those for the rest of the left ventricle (2.73 ± 1.27 versus 2.22 ± 0.83; p = 0.011) and lateral wall (2.73 ± 1.27 versus 1.44 ± 0.72; p < 0.001). All patients with sentinel region average multiparametric strain Z-scores less than two standard deviations (n = 6) experienced complete recovery, whereas 17 of 18 DCM patients with Z-scores greater than two standard deviations experienced incomplete or no contractile recovery.

CONCLUSIONS

Contractile injury in DCM is heterogeneous, with basilar-septal regions injured more than lateral regions. The targeting of early-injury sentinel regions for heightened surveillance with high-resolution metrics of microregional contractile function may accurately predict recovery on medical therapy. A two standard deviation Z-score threshold may predict contractile recovery.

Narrow QRS systolic heart failure: is there a target for cardiac resynchronization?

Cardiac resynchronization therapy has revolutionized the management of systolic heart failure in patients with prolonged QRS during the past 20 years. Initially, the use of this treatment in patients with shorter QRS durations showed promising results, which have since been opposed by larger randomized controlled trials. Despite this, some questions remain, such as, whether correction of mechanical dyssynchrony is the therapeutic target by which biventricular pacing may confer benefit in this group, or are there other mechanisms that need consideration? In addition, novel techniques of cardiac resynchronization therapy delivery such as endocardial and multisite pacing may reduce potential detrimental effects of biventricular pacing, thereby improving the benefit/harm balance of this therapy in some patients.

Imaging of Myocardial Oxidative Metabolism in Heart Failure

Metabolic imaging has a potential for better understanding of pathophysiology of heart failure. C-11 acetate is taken up by the heart, rapidly converted to acetylCoA and readily metabolized to C-11 CO₂ through TCA cycle with oxidative phosphorylation. Thus, the myocardial turnover rate of this tracer is tightly correlated with its clearance of C-11 CO₂, reflecting overall oxidative metabolism. The heart relies on aerobic oxidative substrate for the generation of ATP, which is required to maintain its contractile function. The progression to heart failure is associated with a gradual decline in the activity of mitochondrial respiratory pathways, leading to diminished capacity for ATP production. The work metabolic index can also be estimated by the combination of C-11 acetate PET and hemodynamics by echocardiography, the metabolic index is a significant marker to understand the pathophysiology of heart failure as well as myocardial oxidative metabolism.

Prevalence of ventricular discordance and its relation to functional capacity in idiopathic dilated cardiomyopathy

INTRODUCTION

Although left ventricular (LV) dilatation is the most distinguishing morphologic feature of idiopathic dilated cardiomyopathy (IDC), right ventricular (RV) dilatation may variably contribute to total cardiac enlargement. The prevalence and functional importance of the relative degree of left and right ventricular dilatation has not been comprehensively studied using cardiac magnetic resonance imaging (MRI).

METHODS

Our prospective study included 58 consecutive IDC patients with a LV ejection fraction <40% and NYHA functional class > or =2. MRI was performed with a 1.5 Tesla scanner for RV and LV dimensional and functional analysis. Cardiopulmonary exercise testing was used for evaluation of exercise capacity. Patients were grouped into tertiles based on the distribution of LV end-diastolic volume.

RESULTS

Compared to control subjects a considerable heterogeneity in the relative degree of left and right ventricular dilatation was noted in IDC patients. Within the entire patient group, a strong correlation between the degree of ventricular volume discordance and the extent of LV enlargement was observed (r = 0.8; P < 0.001). Tertile analysis revealed that the LV/RV volume ratio significantly differed in the three subgroups of patients (1.0 +/- 0.3 vs. 1.5 +/- 0.4 vs. 2.1 +/- 0.9; P < 0.001). Only weak correlations between MRI data and patients' functional capacity were found. LV ejection fraction was identified as the only independent predictor of maximum oxygen consumption in our setting.

CONCLUSION

In IDC patients the degree of ventricular volume discordance is strongly related to the extent of left ventricular enlargement. However, comprehensive biventricular assessment of cardiac function by MRI adds little to our understanding of the cardiac mechanisms limiting exercise tolerance when compared to exclusive left ventricular measurements.

Magnetic resonance imaging-based multiparametric systolic strain analysis and regional contractile heterogeneity in patients with dilated cardiomyopathy

BACKGROUND

Myocardial systolic strain patterns in dilated cardiomyopathy are considered non-homogeneous but have not been investigated with magnetic resonance imaging (MRI)-based multiparametric systolic strain analysis. Left ventricular (LV) 3-dimensional (3D) multiparametric systolic strain analysis is sensitive to regional contractility and is generated from sequential MRI of tissue-tagging gridline-point displacements.

METHODS

Sixty normal human volunteers underwent MRI-based 3D systolic strain analysis to supply normal average and standard deviation values for each of three strain parameters at each of 15,300 individual LV grid-points. Patient-specific multiparametric systolic strain data from each dilated cardiomyopathy patient (n = 10) were then subjected to a point-by-point comparison (n = 15,300 LV points) to the normal strain database for three individual strain components (45,900 database comparisons per patient). The resulting composite multiparametric Z-score values (standard deviation from normal average) were color contour mapped over patient-specific 3D LV geometry to detect the normalized regional contractile patterns associated with dilated cardiomyopathy.

RESULTS

Average multiparametric strain Z-score values varied significantly according to ventricular level (p = 0.001) and region (p = 0.003). Apical Z-scores were significantly less than those in both the base (p = 0.037) and mid-ventricle (p = 0.002), whereas anterolateral wall Z-scores were less than those in the anteroseptal (p = 0.023) and posteroseptal walls (p = 0.028).

CONCLUSIONS

MRI-based multiparametric systolic strain analysis suggests that myocardial systolic strain in patients with dilated cardiomyopathy has a heterogeneous regional distribution and, on average, falls almost 2 standard deviations from normal.

Cardiotropin-1 and Myocardial Strain Change Heterogeneously in Cardiomyopathy

BACKGROUND

The pacing model of heart failure produces heterogeneous changes in wall stress and myocyte diameter. The purpose of this study was to measure regional changes in cardiotrophin-1 (CT-1), a cytokine thought to play a role in LV remodeling, and regional changes in LV strain as measured with magnetic resonance imaging.

MATERIALS AND METHODS

Dilated cardiomyopathy was induced in nine mongrel dogs over 4 wk by rapid pacing using a right ventricular epicardial lead. Baseline CT-1 was measured from an apical myocardial biopsy, and regional CT-1 was measured from anterior, lateral, inferior, and septal walls after the induction of heart failure and in six control dogs. Tissue tagged images were divided into similar regions and minimal principal strain (MPS), ejection fraction, and ventricular volumes were compared after induction of heart failure.

RESULTS

After induction of heart failure, LV ejection fraction and end-diastolic volume differed significantly from baseline (P < 0.01 and P = 0.02, respectively). Additionally, regional CT-1 and MPS were significantly different (P < 0.01 for both). Cardiotrophin-1 increased significantly in the inferior and septal walls (both P < 0.01) but not in the anterior or lateral walls (both P = NS). Minimum principal strain decreased significantly in the inferior and septal walls (both P < 0.01) but not in the anterior or lateral walls (both P = NS).

CONCLUSION

The pacing model of heart failure produces heterogeneous changes in regional CT-1 and wall motion as measured by MPS. The greatest regional changes are closest to the pacemaker site: the inferior and septal walls. These differences in regional CT-1 may account for previously noted myocyte hypertrophy and preserved ventricular function in these regions.

Decreased left ventricular torsion and untwisting in children with dilated cardiomyopathy

The purpose of this study was to analyze left ventricular (LV) torsion and untwisting, and to evaluate the correlation between torsion and other components of LV contraction in children with dilated cardiomyopathy (DCM). Segmental and global rotation, rotational rate (Vrot) were measured at three levels of LV using the two dimensional (2D) speckle tracking imaging (STI) method in 10 DCM patients (range 0.6-15 yr, median 6.5 yr, 3 females) and 17 age- and sex-matched normal controls. Global torsion was decreased in DCM (peak global torsion; 10.9 +/- 4.6 degrees vs. 0.3 +/- 2.1 degrees , p<0.001). Loss of LV torsion occurred mainly by the diminution of counterclockwise apical rotation and was augmented by somewhat less reduction in clockwise basal rotation. In DCM, the normal counterclockwise apical rotation was not observed, and the apical rotation about the central axis was clockwise or slightly counterclockwise (peak apical rotation; 5.9 +/- 4.1 degrees vs. -0.9 +/- 3.1 degrees , p<0.001). Systolic counterclockwise Vrot and early diastolic clockwise Vrot at the apical level were decreased or abolished. In DCM, decreased systolic torsion and loss of early diastolic recoil contribute to LV systolic and diastolic dysfunction. The STI method may facilitate the serial evaluation of the LV torsional behavior in clinical settings and give new biomechanical concepts for better management of patients with DCM.

MRI to assess arrhythmia and cardiomyopathies: relationship to echocardiography

Cardiomyopathies are a group of diseases that are associated with myocardial dysfunction and/or arrhythmia due to abnormalities of the myocardium. Echocardiography is the most commonly used method for functional evaluation and classification of cardiomyopathy since it is widely available. Magnetic resonance imaging (MRI) has recently emerged as a well-validated diagnostic tool for the understanding and treatment of these conditions. Morphological and functional information can be achieved with a high level of accuracy and reproducibility. This article reviews the applications of MRI in relationship to echocardiography for the diagnosis of cardiomyopathy and arrhythmogenic conditions of the heart.

Left Ventricle Volume Affects the Result of Mitral Valve Surgery for Idiopathic Dilated Cardiomyopathy to Treat Congestive Heart Failure

BACKGROUND

Mitral valve surgery is a recommended treatment for congestive heart failure; however, its effect for idiopathic dilated cardiomyopathy (DCM) with an extremely enlarged left ventricle (LV) is not well documented. We examined our long-term results of mitral valve surgery for idiopathic dilated cardiomyopathy.

METHODS

Fifty-five patients of idiopathic dilated cardiomyopathy have undergone mitral valve surgery to treat intractable congestive heart failure since 1998. Forty-two patients were male with an average age of 55. Preoperative New York Heart Association functional class was III in 25, IV in 30, and 19 were dependent on inotropic infusion. The mitral valve was repaired in 37 patients and replaced in 18. The tricuspid valve was repaired in 35 patients and replaced in 3. We divided 46 elective cases into two groups by LV end-systolic volume index.

RESULTS

Postoperatively, an intraaortic balloon pump was required in 2 patients and a left ventricular assist device in 1; both were emergent cases. Hospital mortality was noted 4.3% in elective cases (2 of 46) and 14.5% in overall cases (8 of 55). One-year, 3-year, and 5-year survival rate of elective cases was 73.3%, 58.2%, and 51.7%, respectively. Left ventricle size has decreased and LV contractility has increased in a small LV group year by year, but those in a large LV volume group have not changed subsequently after surgery. There was a significant difference noted in the survival rate of the two groups divided by LV end-systolic volume index.

CONCLUSIONS

Mitral valve surgery for idiopathic dilated cardiomyopathy to treat end-stage heart failure is relatively safe and effective in elective status. However, isolated mitral reconstruction without any other type of surgery may not suffice for an extremely enlarged LV.

Does Myocardial Fibrosis Hinder Contractile Function and Perfusion in Idiopathic Dilated Cardiomyopathy? PET and MR Imaging Study

PURPOSE

To prospectively evaluate, by using positron emission tomography (PET) and magnetic resonance (MR) imaging, the interrelationships between regional myocardial fibrosis, perfusion, and contractile function in patients with idiopathic dilated cardiomyopathy (DCM).

MATERIALS AND METHODS

The study protocol was approved by the hospital ethics committee, and all subjects gave written informed consent. Sixteen patients with idiopathic DCM (mean age, 54 years +/- 11 [standard deviation]; nine men) and six healthy control subjects (mean age, 28 years +/- 2; five men) were examined with PET and MR tissue tagging. Oxygen 15-labeled water and carbon monoxide were used as tracers at PET to assess myocardial blood flow (MBF) and the perfusable tissue index (PTI), which is inversely related to fibrosis. MBF was determined at rest and during pharmacologically induced hyperemia. Maximum circumferential shortening (E(cc)) was determined with MR tissue tagging. Student t tests were performed for comparison of data sets, and linear regression was used to investigate the association between parameters.

RESULTS

Mean global hyperemic MBF (2.23 mL/min/mL +/- 0.73), E(cc) (-10.5% +/- 2.9), and PTI (0.95 +/- 0.10) were lower in the patients with DCM than in the control subjects (4.33 mL/min/mL +/- 0.85, -17.4% +/- 0.6, and 1.09 +/- 0.12, respectively; P < .05 for all). In the patients with DCM, regional PTI was related to E(cc) (r = -0.21, P = .009) but not to resting or hyperemic MBF. Furthermore, regional E(cc) was correlated to both resting (r = -0.28, P = .004) and hyperemic MBF (r = -0.29, P < .001). In addition, the ratio of left ventricular end-diastolic volume to mass, as a reflection of wall stress, was related to global hyperemic MBF (r = -0.52, P = .047) and to global E(cc) (r = 0.69, P = .003).

CONCLUSION

In idiopathic DCM, the extent of myocardial fibrosis is related to the impairment in contractile function, whereas fibrosis and perfusion do not seem to be interrelated. The degree of impairment of hyperemic myocardial perfusion is related to contractility and end-diastolic wall stress.

Head-to-head comparison of indices of left ventricular contractile reserve assessed by high-dose dobutamine stress echocardiography in idiopathic dilated cardiomyopathy: five-year follow up

OBJECTIVE

To compare head to head the indices of left ventricular contractile reserve assessed by high-dose dobutamine in the five-year prognosis of patients with idiopathic dilated cardiomyopathy.

DESIGN AND SETTING

Prospective study in a tertiary care centre.

PATIENTS

63 consecutive patients with idiopathic dilated cardiomyopathy.

INTERVENTIONS

High-dose dobutamine stress echocardiography was performed in progressive stages lasting 5 min each. Wall motion score index, ejection fraction, cardiac power output and end systolic pressure to volume ratio were evaluated as indices of left ventricular contractility.

MAIN OUTCOME MEASURE

Five-year cardiac mortality.

RESULTS

During the follow up of 59 patients, 27 (45.8%) died of cardiac causes. According to Kaplan-Meier and receiver operating characteristic analyses all indices of contractile reserve differentiated patients with respect to cardiac death. Wall motion score index achieved the best separation (log rank 21.75, p < 0.0001, area under the curve 0.84), followed by change in ejection fraction (log rank 11.25, p = 0.0008, area under the curve 0.79), end systolic pressure to volume ratio (log rank 14.32, p = 0.0002, area under the curve 0.75) and cardiac power output (log rank 9.84, p = 0.0017, area under the curve 0.71). Cox's regression model identified wall motion score index as the only independent predictor of cardiac death.

CONCLUSIONS

These data show that all examined indices of left ventricular contractile reserve are predictive of five-year prognosis, but change in wall motion score index may have the greatest prognostic potential.

Global and regional myocardial oxygen consumption and blood flow in severe cardiomyopathy with left bundle branch block

OBJECTIVE

In patients with dilated cardiomyopathy (DCM), left bundle branch block (LBBB) is a common finding. The characteristic feature is an asynchronous septal wall motion and most frequently a delay of the lateral and/or posterior wall segments. With the onset of cardiac resynchronization therapy, there is a focus on the specific pathophysiology of a LBBB. However, quantitative data on regional myocardial oxygen consumption (MVO(2)) and blood flow (MBF) are missing.

METHODS

We studied 31 patients with severe DCM and LBBB (ejection fraction 22.1+/-7.1%) and 14 patients with mild to moderate DCM without LBBB (ejection fraction 46.7+/-7.9%). Global and regional MVO(2) as well as MBF were determined from a dynamic (11)C-acetate positron emission tomography (PET) study.

RESULTS

Global MVO(2) and MBF were lower in the DCM group with LBBB than in the control group (P<0.05). Regionally, the LBBB group revealed a higher (P<0.05) MVO(2) and MBF in the lateral wall than in the other walls. The control group did not show significant differences between the myocardial walls and demonstrated a smaller variability of the parameters.

CONCLUSION

DCM patients with LBBB exhibit a more heterogeneous distribution of MVO(2) and MBF among the myocardial walls than DCM patients without LBBB. Due to the LBBB associated electromechanical alterations, the highest regional values of MVO(2) and MBF are found in the lateral wall.

Segmental wall motion abnormalities in idiopathic dilated cardiomyopathy and their effect on prognosis

There is considerable variability in segmental wall motion abnormalities and in the prognosis of idiopathic dilated cardiomyopathy (IDC). Radionuclide ventriculography with Fourier analysis was performed in 107 patients with angiographically proved IDC. Amplitude analysis located the wall motion abnormalities. Using phase analysis in the left and right ventricles, the interventricular delay between the mean phase of the right and left ventricles was used to assess interventricular dyssynchrony and SDs of the mean phase in each ventricle was used to assess intraventricular dyssynchrony. Hypokinesis was global in 56 patients (52%) and localized in the anteroseptal wall in 34 (32%), the inferior wall in 12 (11%), the anteroseptal and inferior walls in 2 (2%), and the lateral wall in 3 (3%). Patients with localized wall motion abnormalities had larger left ventricular (LV) end-diastolic diameters (70 +/- 9 vs 66 +/- 8 mm, p = 0.009) and lower LV ejection fractions (25 +/- 9% vs 31 +/- 12%, p = 0.005). Intraventricular dyssynchrony was lower in patients with global hypokinesis (SD of LV mean phase 67 +/- 35 vs 48 +/- 22 ms, p = 0.002). With a follow-up of 27 +/- 23 months, increased SD of the LV phase (p = 0.005), decreased right ventricular ejection fraction (p = 0.006), decreased LV ejection fraction (p = 0.04), and localized wall motion abnormality (p = 0.009) were independent predictors of cardiac death or worsening heart failure leading to heart transplantation. Thus, segmental wall motion abnormalities are frequent in IDC and are associated with severe systolic dysfunction and a worse prognosis.

PET abnormalities in patients with nonischemic cardiomyopathy

BACKGROUND

The abnormalities in dilated cardiomyopathy (DCM) are generally considered diffuse and to affect the left ventricle in a global manner. However, regional wall motion abnormalities and metabolic defects may also occur to varying, but unclear degrees. QRS width and metabolic defects on positron emission tomography (PET) correlate with survival. We sought to ascertain the prevalence of regional defects in DCM by multiple imaging modalities and to establish the relationship between QRS width and these defects.

METHODS

In consecutive patients with advanced nonischemic DCM, undergoing cardiac transplant evaluation, we reviewed multiple imaging modalities (PET, 2-dimensional echocardiography, and radionuclide ventriculography) to quantify the incidence of regional metabolic and wall motion abnormalities and correlate them with clinical and electrocardiographic parameters.

RESULTS

Of 44 patients studied, PET imaging revealed scar in 91% of patients, with a mean of 25 +/- 18% of the left ventricle involved, predominantly in the distribution of the left anterior descending artery. Regional wall motion abnormalities occurred in 51% of patients who underwent echocardiography and 59% of patients who underwent nuclear scintigraphy (with only 70% concordance). QRS duration on the surface electrocardiogram correlated positively with the degree of scarring (r=.52, P=.0007).

CONCLUSIONS

The presence of scar (matched perfusion and metabolic defects) on PET scanning in patients with advanced DCM is not always indicative of coronary disease. Thus coronary angiography is usually required to define the etiology of systolic dysfunction. The extent of scar correlates with QRS duration. This may have implications for the application of cardiac resynchronization therapy.

Echocardiographic assessment of regional ventricular function after device-based change of left ventricular shape

We assessed the effects of implantation of Myosplint (Myocor, Maple Grove, Minn), a device that changes left ventricular (LV) cross-sectional shape from circular to bilobar, on regional LV function. A total of 10 open-chest dogs with tachycardia-induced cardiomyopathy were studied before and after Myosplint implantation. LV cross-sectional epicardial echocardiography at the papillary muscle level was performed along with acquisition of hemodynamic data. LV normalized thickening, fractional thickening, end-diastolic thickness, and end-diastolic curvatures were calculated for 10 LV segments. Myosplint implantation did not affect LV hemodynamics, but decreased average end-diastolic curvature (P <.0001) and increased its segmental heterogeneity (P <.0001). There was no change in average fractional thickening, whereas normalized thickening increased (P =.05). In contrast, segmental heterogeneity of both normalized and fractional thickening increased (P =.02 and P =.01, respectively). Structural modeling confirmed that Myosplint implantation increases regional stress heterogeneity and curvature heterogeneity. LV cross-sectional shape markedly affects regional LV performance.

Passive external cardiac constraint improves segmental left ventricular wall motion and reduces akinetic area in patients with non-ischemic dilated cardiomyopathy

OBJECTIVE

To verify changes in left ventricular (LV) volumes and regional myocardial wall motion after implantation of a textile cardiac support device (CSD) for passive external constraint in non-ischemic dilated cardiomyopathy.

METHODS

In nine male patients participating in a non-randomized clinical trial LV volumes were determined and the segmental LV wall motion was studied by contrast-enhanced electron-beam CT in a sectionwise manner at three ventricular levels (base, middle and apex of ventricle) before and 32+/-6 months after CSD implantation. In 16 myocardial segments ejection fraction and wall thickening were measured semiautomatically after drawing the myocardial contours. The wall motion score index was calculated based on semiquantitative visual grading in each segment.

RESULTS

The global LV volumes decreased significantly from 304.3 +/- 90.9 to 231.5 +/- 103.9 ml at end-diastole and from 239.7 +/- 83.7 to 164.0 +/- 97.7 at end-systole (P<0.05). Overall ejection fraction increased from 14.8 +/- 8.2 to 25.7 +/- 17.1% (P<0.05). A segment-by-segment analysis demonstrated a significant increase of regional ejection fraction in the basal myocardium as well as in the mid-inferior, mid-inferolateral, and mid-anterolateral myocardium. Overall wall thickening increased from 16.4 +/- 13.3 to 24.2 +/- 18.1% (P<0.05), but without significant differences in a segment-by-segment comparison. The mean wall motion score index improved from 2.70 +/- 0.26 to 2.20 +/- 0.71 (P<0.05), with an increased wall motion in eight (89%) patients. A section-by-section analysis demonstrated significantly improved wall motion in the inferior and lateral segments at each ventricular level. Postoperatively, the number of akinetic and markedly hypokinetic segments decreased significantly (P<0.05) from 56 (39%) to 26 (18%) and from 76 (53%) to 56 (37%), respectively.

CONCLUSION

CSD implantation improves segmental wall motion, predominantly in the inferior and lateral myocardium, and reduces the number of akinetic and hypokinetic segments.

Noninvasive assessment of cardiac mechanics and clinical outcome after partial left ventriculectomy

BACKGROUND

Partial left ventriculectomy (PLV) was developed as a therapy for end-stage heart failure, but results were variable with few a priori predictors of outcome. Little is known about its effects on myocardial mechanics and their relation to clinical outcome.

METHODS

Twenty-four dilated cardiomyopathy patients underwent cardiac magnetic resonance imaging (MRI) before PLV, and 3 and 12 months after surgery. Left ventricular (LV) circumferential shortening and wall stress were computed at three short-axis levels. Exploratory outcome analysis grouped patients according to the timing of adverse cardiac events postsurgery.

RESULTS

LV mass and volume were decreased at each postsurgical time point (all p < 0.01). At 3 months, regional wall stress was reduced at all short-axis levels; but by 12 months stress was reduced from baseline only at the apex. Circumferential shortening was increased significantly at both postsurgical time points at each level. On average, septal shortening was negative (stretching) before surgery, but increased significantly, and was positive, postsurgery. Exploratory outcome analysis found that negative values of basal septum circumferential shortening before surgery increased the probability of event-free survival beyond 6 months.

CONCLUSIONS

Regional heterogeneity of LV myocardial function, associated with dilated cardiomyopathy, was diminished after PLV but was also related to patient outcome. MRI with tissue tagging is useful for assessing the efficacy of surgical therapies for congestive heart failure.

Abnormal contractile responses during dobutamine stress echocardiography in patients with idiopathic dilated cardiomyopathy

BACKGROUND

In chronic heart failure augmented wall stress leads to increased energy demand. Supply, however, may be reduced due to coronary vasoconstriction and endothelial dysfunction. This might lead to a mismatch between demand and supply. In the present study we further explored the effect of increased demand during dobutamine stress echocardiography.

METHODS AND RESULTS

Sixteen patients with idiopathic dilated cardiomyopathy (mean age 44+/-13 years, New York Heart Association class II-III, mean left ventricular ejection fraction 0.27+/-0.10) underwent dobutamine stress echocardiography (5-40 microg/min per kg bodyweight+atropine if required). Wall motion and thickening was assessed in 16 segments using a four-point scale. Eleven patients (69%) showed regions with worsening of wall motion or a biphasic response during dobutamine infusion. Of the remaining five patients one patient did not show any wall motion changes and one patient showed a partial improvement while only in three patients wall motion improvement in the whole heart was found.

CONCLUSION

A majority of patients with idiopathic dilated cardiomyopathy showed decreased wall motion during increased demand, i.e. ischemia-like myocardial contractile responses during dobutamine stress echocardiography. These findings further support the concept that an energy mismatch between demand and supply might play a pathophysiological role in idiopathic dilated cardiomyopathy.

Regional myocardial metabolic rate of oxygen measured by O2-15 inhalation and positron emission tomography in patients with cardiomyopathy

BACKGROUND

Positron emission tomography (PET) metabolic studies have investigated the pathways involved in fatty acid, glucose, and oxidative metabolism in cardiomyopathy and the impairments that occur in the damaged myocardium, but none have provided absolute quantitative variables. Recently, quantitative measurements of the metabolic rate of oxygen (MMRO2) and oxygen extraction fraction (OEF) using O2-15-labeled oxygen gas have been validated in animals and healthy volunteers. The purposes of the current study were to measure MMRO2 and OEF in cardiomyopathy with left ventricular (LV) dysfunction.

METHODS

The authors selected 25 study participants: 16 patients (10 with ischemic and 6 with dilated) cardiomyopathy with LV dysfunction, and 9 healthy volunteers. As evaluated by echocardiography, LV ejection fraction (LVEF) was decreased in patients (35%+/-9% vs. 65%+/-5%, P<0.01). The PET protocol consisted of transmission, C O2-15 static, H2 O-15 dynamic, and O2-15 gas inhalation steady state scans. An entire myocardial region of interest was drawn to encompass the entire LV myocardium on three midventricular slices in each participant.

RESULTS

Data showed in patients with dilated cardiomyopathy significant reductions of MMRO2 (0.051+/-0.02 ml x min(-1) x g(-1) vs. 0.108+/-0.02 ml x min(-1) x g(-1), p = 0.01) and OEF (0.55+/-0.15 vs. 0.71+/-0.08, P = 0.01) when compared with healthy volunteers. Furthermore, OEF decreased significantly in lateral and inferior walls. Significant correlations were observed among OEF and the rate-pressure product (RPP) (P = 0.02), LVEF (P<0.001), MMRO2 and RPP (P = 0.04), and LVEF (P = 0.05). In patients with ischemic cardiomyopathy, MMRO2 was significantly reduced (0.039+/-0.02 ml x min(-1) x g(-1) vs. 0.108+/-0.02 ml x min(-1) x g(-1); p = 0.005) but not OEF (0.63+/-0.2 vs. 0.71+/-0.08; P = NS), when compared with healthy volunteers. Significant correlations were observed among OEF and RPP (P = 0.03), LVEF (P = 0.002), MMRO2 and RPP (P<0.01), and LVEF (P = 0.03).

CONCLUSIONS

These data show that O2-15 gas inhalation and PET allow myocardial MMRO2 and OEF to be measured in patients with cardiomyopathy.

Left ventricular regional wall motion, ejection fraction, and geometry after partial left ventriculectomy. Influence of associated mitral valve repair

OBJECTIVE

Left partial ventriculectomy has been proposed for treatment of heart failure. We investigated the effects of isolated left partial ventriculectomy and left partial ventriculectomy associated with mitral annuloplasty on refractory heart failure due to idiopathic dilated cardiomyopathy.

METHODS

Nineteen patients underwent partial left partial ventriculectomy associated with mitral annuloplasty and six patients isolated left partial ventriculectomy. In two patients the left partial ventriculectomy associated with mitral annuloplasty was combined with tricuspid annuloplasty. We evaluated before and after the surgery (24+/-14 days): the functional class, left ventricular ejection fraction (LVEF), right ventricular ejection fraction (EF), regional wall motion, hemodynamics, mitral regurgitation, left ventricular geometry and coronary angiography.

RESULTS

For the overall group LVEF improved from 14.5+/-8.0 to 30.3+/-12.2% (P<0.0002) and right ventricular EF from 21.2+/-7.1 to 28.4+/-8.3% (P<0.002). In patients who underwent left partial ventriculectomy associated with mitral annuloplasty LVEF increased from 14.5+/-8.6 to 29.5+/-12.2% (P<0. 002). Isolated left partial ventriculectomy increased LVEF from 13. 5+/-7.5 to 31.5+/-11.1% (P<0.04). Distal segments of marginal branches of the circumflex artery were not visualized by coronary angiography. Left partial ventriculectomy associated with mitral annuloplasty reduced the wedge pressure from 25.0+/-12.1 to 18.0+/-7. 0 mmHg (P<0.03) and increased cardiac output from 3.8+/-0.8 to 4. 6+/-1.1 l/min (P<0.004), while isolated left partial ventriculectomy increased cardiac output from 3.7+/-1.0 to 4.8+/-1.3 l/min (P<0.03). Regional wall motion increment was more evident in anterolateral region from 4.2+/-6.8 to 14+/-8.3% (P<0.002) except in two patients. Left ventricular geometry changed in most patients, but a homogeneous pattern was not identified. Seven patients died during a mean follow-up of 546+/-276 days. Survivors had improvement in functional class. Augmentation of LVEF >5% was associated with a favorable clinical outcome with improvement in clinical status without death.

CONCLUSIONS

Effects of left partial ventriculectomy are not necessarily dependent upon reduction of mitral regurgitation or changes in left ventricular geometry. However, risk of death after the surgery must be reduced for a clinical application.

Regional myocardial blood flow reserve impairment and metabolic changes suggesting myocardial ischemia in patients with idiopathic dilated cardiomyopathy

OBJECTIVES

We performed positron emission tomography (PET) to evaluate myocardial ischemia in patients with idiopathic dilated cardiomyopathy (IDC).

BACKGROUND

Patients with IDC have anatomically normal coronary arteries, and it has been assumed that myocardial ischemia does not occur.

METHODS

We studied 22 patients with IDC and 22 control subjects using PET with nitrogen-13 ammonia to measure myocardial blood flow (MBF) at rest and during dipyridamole-induced hyperemia. To investigate glucose metabolism, fluorine-18 deoxyglucose (18FDG) was used. For imaging of oxygen consumption, carbon-11 acetate clearance rate constants (k(mono)) were assessed at rest and during submaximal dobutamine infusion (20 microg/kg body weight per min).

RESULTS

Global MBF reserve (dipyridamole-induced) was impaired in patients with IDC versus control subjects (1.7 +/- 0.21 vs. 2.7 +/- 0.10, p < 0.05). In patients with IDC, MBF reserve correlated with left ventricular (LV) systolic wall stress (r = -0.61, p = 0.01). Furthermore, in 16 of 22 patients with IDC (derived by dipyridamole perfusion) mismatch (decreased flow/increased 18FDG uptake) was observed in 17 +/- 8% of the myocardium. The extent of mismatch correlated with LV systolic wall stress (r = 0.64, p = 0.02). The MBF reserve was lower in the mismatch regions than in the normal regions (1.58 +/- 0.13 vs. 1.90 +/- 0.18, p < 0.05). During dobutamine infusion k(mono) was higher in the mismatch regions than in the normal regions (0.104 +/- 0.017 vs. 0.087 +/- 0.016 min(-1), p < 0.05). In the mismatch regions 18FDG uptake correlated negatively with rest k(mono) (r = -0.65, p < 0.05), suggesting a switch from aerobic to anaerobic metabolism.

CONCLUSIONS

Patients with IDC have a decreased MBF reserve. In addition, low MBF reserve was paralleled by high LV systolic wall stress. These global observations were associated with substantial myocardial mismatch areas showing the lowest MBF reserves. In geographically identical regions an abnormal oxygen consumption pattern was seen together with a switch from aerobic to anaerobic metabolism. These data support the notion that regional myocardial ischemia plays a role in IDC.

Initial clinical experience of real-time three-dimensional echocardiography in patients with ischemic and idiopathic dilated cardiomyopathy

The geometry of the left ventricle in patients with cardiomyopathy is often sub-optimal for 2-dimensional ultrasound when assessing left ventricular (LV) function and localized abnormalities such as a ventricular aneurysm. The aim of this study was to report the initial experience of real-time 3-D echocardiography for evaluating patients with cardiomyopathy. A total of 34 patients were evaluated with the real-time 3D method in the operating room (n = 15) and in the echocardiographic laboratory (n = 19). Thirteen of 28 patients with cardiomyopathy and 6 other subjects with normal LV function were evaluated by both real-time 3-D echocardiography and magnetic resonance imaging (MRI) for obtaining LV volumes and ejection fractions for comparison. There were close relations and agreements for LV volumes (r = 0.98, p <0.0001, mean difference = -15 +/- 81 ml) and ejection fractions (r = 0.97, p <0.0001, mean difference = 0.001 +/- 0.04) between the real-time 3D method and MRI when 3 cardiomyopathy cases with marked LV dilatation (LV end-diastolic volume >450 ml by MRI) were excluded. In these 3 patients, 3D echocardiography significantly underestimated the LV volumes due to difficulties with imaging the entire LV in a 60 degrees x 60 degrees pyramidal volume. The new real-time 3D echocardiography is feasible in patients with cardiomyopathy and may provide a faster and lower cost alternative to MRI for evaluating cardiac function in patients.

Prognostic utility of myocardial blood flow assessed by N-13 ammonia positron emission tomography in patients with idiopathic dilated cardiomyopathy

Previous studies in patients with idiopathic dilated cardiomyopathy (IDC) have suggested that myocardial perfusion is impaired and spatially heterogeneous in such cases. Our objective was to identify any association between an abnormality in myocardial perfusion and the prognosis of patients with IDC. We collected data on N-13 ammonia positron emission tomography (PET) studies performed in 26 patients with IDC (9 nonsurvivors, 17 survivors) and in 8 normal control subjects. Regional myocardial blood flow (rMBF) was quantified using N-13 ammonia positron emission tomography and the Simple flow model. The spatial heterogeneity of myocardial perfusion was assessed by calculating the coefficient of variance of rMBF. Mean rMBF of the survivors was significantly lower (0.54 +/- 0.13 ml/min/g) than that of control subjects (0.66 +/- 0.06 ml/min/g) (p = 0.03 vs control), but did not differ significantly between nonsurvivors (0.58 +/- 0.15 ml/min/g) and control subjects. The coefficient of variance of rMBF was significantly higher in nonsurvivors than in either survivors or control subjects (0.24 +/- 0.08 vs 0.15 +/- 0.08, p = 0.007, and 0.16 +/- 0.05, p = 0.03, respectively). The probability of 3-year survival (Kaplan-Meier method) was 33.0% in subjects whose coefficient of variance of rMBF was above the median compared with 90.0% in subjects whose coefficient of variance of rMBF was below the median (p = 0.01). The probability of 3-year survival did not differ among subjects whose mean rMBF was above versus below the median (61.5% vs 62.9%, respectively). The results suggest that the prognosis of patients with IDC is associated with the spatial heterogeneity of myocardial perfusion, not with initial absolute rMBF.

Left ventricular function and endomyocardial biopsy in early and advanced dilated cardiomyopathy

We evaluated left ventricular function and endomyocardial biopsy in 20 patients with early and advanced dilated cardiomyopathy, with the purpose of assessing the correlation between histologic variables and systolic and diastolic filling indexes. Group 1 included 10 patients with no clinical history of heart failure and left ventricular ejection fraction > or = 45% and group 2, 10 patients with a clinical history of heart failure and left ventricular ejection fraction <45%. Group 1 showed lower left ventricular end-systolic and end-diastolic volumes indexes (49+/-14 versus 86+/-23 ml/m2, P<0.001; 98+/-25 versus 127+/-35 ml/m2, P=0.049), higher left ventricular ejection fraction (50+/-4 versus 32+/-4%, P<0.001) and lower coefficient of variation of percentage shortening of left ventricular transverse hemiaxes (0.3+/-0.1 versus 0.5+/-0.1, P=0.001) compared with group 2. Group 1 had higher A wave peak velocity (78+/-18 versus 60+/-20 cm/s, P=0.048), lower E/A ratio (0.9+/-0.3 versus 1.5+/-0.6, P=0.02) and slower E wave deceleration time (204+/-51 versus 155+/-50 ms, P=0.047) compared with group 2. Semiquantitative histologic scores did not differ significantly between groups. There was no significant correlation between histologic variables and left ventricular systolic and diastolic indexes. Thus, dilated cardiomyopathy shows borderline to severe left ventricular systolic impairment and distinct left ventricular diastolic filling abnormalities, according to the clinical stage. This study suggests a marked dissociation between histologic findings and functional abnormalities in early and advanced dilated cardiomyopathy.