Electromechanical relationship in hypertrophic cardiomyopathy

Cardiomyopathies and a brief insight into DOX-induced cardiomyopathy

BACKGROUND

Cardiomyopathy is a heterogeneous group of myocardial disorders characterized by structural and functional abnormalities of the heart muscle. It is classified into primary (genetic, mixed, or acquired) and secondary categories, resulting in various phenotypes including dilated, hypertrophic, and restrictive patterns. Hypertrophic cardiomyopathy, the most common primary form, can cause exertional dyspnea, presyncope, and sudden cardiac death. Dilated cardiomyopathy typically presents with heart failure symptoms, while restrictive cardiomyopathy is rarer and often associated with systemic diseases. Diagnosis involves a comprehensive evaluation including history, physical examination, electrocardiography, and echocardiography. Treatment options range from pharmacotherapy and lifestyle modifications to implantable cardioverter-defibrillators and heart transplantation in refractory cases.

MAIN BODY

Anthracyclines, particularly doxorubicin, have emerged as crucial components in cancer treatment, demonstrating significant antitumor activity across various malignancies. These drugs have become standard in numerous chemotherapy regimens, improving patient outcomes. However, their use is associated with severe cardiotoxicity, including cardiomyopathy and heart failure. The mechanisms of anthracycline action and toxicity are complex, involving DNA damage, iron-mediated free radical production, and disruption of cardiovascular homeostasis. Doxorubicin-induced cardiomyopathy (DIC) is a severe complication of cancer treatment with a poor prognosis and limited effective treatments. The pathophysiology of DIC involves multiple mechanisms, including oxidative stress, inflammation, mitochondrial damage, and calcium homeostasis disorder. Despite extensive research, no effective treatment for established DIC is currently available. Dexrazoxane is the only FDA-approved protective agent, but it has limitations. Recent studies have explored various potential therapeutic approaches, including natural drugs, endogenous substances, new dosage forms, and herbal medicines. However, the lack of experimental models incorporating pre-existing cancer limits the understanding of DIC pathophysiology and treatment efficacy.

CONCLUSION

Cardiomyopathy, whether primary or secondary, poses a significant clinical challenge due to its varying etiologies and poor prognosis in advanced stages. Anthracycline-induced cardiomyopathy is a severe complication of chemotherapy, with doxorubicin being a notable contributor. Despite advancements in cancer therapies, the cardiotoxic effects of anthracyclines necessitate further investigation into effective preventive strategies and therapeutic interventions to improve patient outcomes.

QRS prolongation is associated with associated with adverse cardiac remodeling in hypertrophic cardiomyopathy

BACKGROUND

Signal-averaged electrocardiogram (SAECG) records myocardial depolarization, and can detect inhomogeneous/slow conduction in fibrotic myocardium, which promotes reentrant ventricular arrhythmias (VAs). Hypertrophic cardiomyopathy (HCM) is associated with a high prevalence of cardiac fibrosis and VAs, but abnormal SAECG has low predictive power for VAs. We hypothesized that HCM-specific structural/electrical remodeling underlies this result.

METHODS

We tested our hypothesis by retrospectively studying HCM patients (n = 73) who underwent transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging within 12 months of SAECG and 12‑lead ECG. Patients were divided into 2 groups (normal-SAECG, abnormal-SAECG) based on filtered-QRS duration (fQRSd), root-mean-square-voltage (RMS40) and low-amplitude (<40 μV) signal of terminal 40 ms of filtered-QRS (late potentials). Abnormal SAECG was defined as fQRSd > 114 ms, RMS40 < 20 μV or LAS40 > 38 ms.

RESULTS

Abnormal SAECG was seen in ∼50 % of HCM patients (37/73). In the abnormal-SAECG group, 78 % (n = 29) only had prolonged fQRSd, and 22 % (n = 8) had prolonged fQRSd plus late potentials (RMS40 < 20 μV or LAS40 > 38 ms). Mean fQRSd and LAS40 were significantly higher in the abnormal-SAECG group. The abnormal-SAECG group had significantly larger LA size, lower global-LV longitudinal systolic strain/strain rate and early-diastolic strain rate by TTE; higher LV-mass index (LVMI) and LV-scar burden by CMR; higher prevalence of repolarization abnormalities on 12‑lead ECG. LVEF and adverse outcomes (VT/VF, heart failure, death) were similar in the 2 groups. Univariate analysis showed that fQRSd is positively correlated with LVMI, LV-scar mass, and negatively correlated with global-LV early diastolic strain rate.

CONCLUSIONS

In HCM, abnormal SAECG is associated with greater structural/electrical LV-remodeling, reflecting a severe global myopathy.

Post-systolic shortening index by echocardiography evaluation of dyssynchrony in the non-dilated and hypertrophied left ventricle

Background

Post-systolic shortening index (PSI) is defined as myocardial shortening that occurs after aortic valve closure, and is an emerging measure of regional LV contractile dysfunction. PSI measurement variability amongst software vendor and its relationship with mechanical dyssynchrony and mechanical dispersion index (MDI) remains unknown. We evaluated PSI by speckle-tracking echocardiography from several vendors in patients with increased left ventricular wall thickness, and associations with MDI.

Methods

This is a prospective cross-sectional study of 70 patients (36 hypertrophic cardiomyopathy [HCM], 18 cardiac amyloidosis and 16 healthy controls) undergoing clinically indicated echocardiography. PSI was measured using QLAB/aCMQ (Philips), QLAB/LV auto-trace (Philips), EchoPAC (GE), Velocity Vector Imaging (Siemens), and EchoInsight (EPSILON) software packages, and calculated as 100%×(post systolic strain–end-systole strain)/post systolic strain.

Results

There was a significant difference in mean PSI among controls 2.1±0.6%, HCM 6.1±2.6% and cardiac amyloidosis 6.8±2.7% (p <0.001). Variations between software vendors were significant in patients with pathologic increases in LV wall thickness (for HCM p = 0.03, for amyloidosis p = 0.008), but not in controls (p = 0.11). Furthermore, there were moderate correlations between PSI and both MDI (r = 0.77) and left ventricular global longitudinal strain (r = 0.69).

Conclusion

PSI was greater in HCM and cardiac amyloidosis patients than controls, and a valuable tool for dyssynchrony evaluation, with moderate correlations to MDI and strain. However, there were significant variations in PSI measurements by software vendor especially in patients with pathological increase in LV wall thickness, suggesting that separate vendor-specific thresholds for abnormal PSI are required.

Toward ECG-based analysis of hypertrophic cardiomyopathy: a novel ECG segmentation method for handling abnormalities

OBJECTIVE

Abnormalities in impulse propagation and cardiac repolarization are frequent in hypertrophic cardiomyopathy (HCM), leading to abnormalities in 12-lead electrocardiograms (ECGs). Computational ECG analysis can identify electrophysiological and structural remodeling and predict arrhythmias. This requires accurate ECG segmentation. It is unknown whether current segmentation methods developed using datasets containing annotations for mostly normal heartbeats perform well in HCM. Here, we present a segmentation method to effectively identify ECG waves across 12-lead HCM ECGs.

METHODS

We develop (1) a web-based tool that permits manual annotations of P, P', QRS, R', S', T, T', U, J, epsilon waves, QRS complex slurring, and atrial fibrillation by 3 experts and (2) an easy-to-implement segmentation method that effectively identifies ECG waves in normal and abnormal heartbeats. Our method was tested on 131 12-lead HCM ECGs and 2 public ECG sets to evaluate its performance in non-HCM ECGs.

RESULTS

Over the HCM dataset, our method obtained a sensitivity of 99.2% and 98.1% and a positive predictive value of 92% and 95.3% when detecting QRS complex and T-offset, respectively, significantly outperforming a state-of-the-art segmentation method previously employed for HCM analysis. Over public ECG sets, it significantly outperformed 3 state-of-the-art methods when detecting P-onset and peak, T-offset, and QRS-onset and peak regarding the positive predictive value and segmentation error. It performed at a level similar to other methods in other tasks.

CONCLUSION

Our method accurately identified ECG waves in the HCM dataset, outperforming a state-of-the-art method, and demonstrated similar good performance as other methods in normal/non-HCM ECG sets.

Left ventricular myocardial deformation pattern, mechanical dispersion, and their relation with electrocardiogram markers in the large population-based STANISLAS cohort: insights into electromechanical coupling

AIMS

Mechanical alterations in patients with electrical conduction abnormalities are reported to have prognostic value in patients with left ventricular asynchrony or long QT syndrome beyond electrocardiogram (ECG) variables. Whether conduction and repolarization patterns derived from ECG are associated with speckle tracking echocardiography parameters in subjects without overt cardiac disease is yet to be investigated. To report ranges of longitudinal deformation according to conduction and repolarization values in a population-based cohort.

METHODS AND RESULTS

One thousand, one hundred, and forty subjects (48.6 ± 14.0 years, 47.7% men) enrolled in the fourth visit of the STANISLAS cohort (Lorraine, France) were studied. Echocardiography strain was performed in all subjects. RR, PR, QRS, and QT intervals were retrieved from digitalized 12-lead ECG. Echocardiographic data were stratified according to quartiles of QRS and QTc duration values. Full-wall global longitudinal strain (GLS) was -21.1 ± 2.5% with a mechanical dispersion (MD) value of 34 ± 12 ms. Absolute GLS value was lower in the longest QRS quartile and shortest QTc quartile (both P < 0.001). Time-to-peak of strain was not significantly different according to QRS duration although significantly higher in patients with higher QTc (P < 0.001). MD was significantly greater in patients with longer QTc (32 ± 12 ms for QTc < 396 ms vs. 36 ± 12 ms for QTc > 421 ms; P = 0.002).

CONCLUSION

Longer QTc is related to increased MD and better longitudinal strain values. In a population-based setting, QRS is not associated with MD, suggesting that echocardiography-based dyssynchrony does not largely overlap with ECG-based dyssynchrony.

How are ECG parameters related to cardiac magnetic resonance images? Electrocardiographic predictors of left ventricular hypertrophy and myocardial fibrosis in hypertrophic cardiomyopathy

Background

Structural myocardial changes in hypertrophic cardiomyopathy (HCM) are associated with different abnormalities on electrocardiographs (ECGs). The diagnostic value of the ECG voltage criteria used to screen for left ventricular hypertrophy (LVH) may depend on the presence and degree of myocardial fibrosis. Fibrosis can cause other changes in ECG parameters, such as pathological Q waves, fragmented QRS (fQRS), or repolarization abnormalities.

Methods

We investigated 146 patients with HCM and 35 healthy individuals who underwent cardiac magnetic resonance imaging (CMR; with late gadolinium enhancement [LGE] in HCM patients) and standard 12‐lead ECGs. On the ECG, depolarization and repolarization abnormalities, the Sokolow–Lyon index, the Cornell index, and the Romhilt–Estes score were evaluated. The left ventricular ejection fraction, volumes, and myocardial mass (LVM) were quantified. Myocardial fibrosis was quantified on LGE images.

Results

The sensitivity of the Romhilt–Estes score was the highest (75%), and this hypertrophy criterion had the strongest correlation with the LVM index (p < .0001; r = .41). The amount of fibrosis was negatively correlated with the Cornell index (p = .015; r = −.201) and the Sokolow–Lyon index (p = .005; r = −.23), and the Romhilt–Estes score was independent of fibrosis (p = .757; r = 0.026). fQRS and strain pattern predicted more fibrosis, while the Cornell index was a negative predictor of myocardial fibrosis (p < .0001). Among others, the strain pattern was an independent predictor of the LVM (p < .0001).

Conclusion

The Romhilt–Estes score is the most sensitive ECG criterion for detecting LVH in HCM patients, as myocardial fibrosis does not affect this criterion. The presence of fQRS and strain pattern predicts myocardial fibrosis.

Early Repolarization Pattern and Left Ventricular Mass in Hypertrophic Cardiomyopathy

BACKGROUND

J-point elevation in the inferior and/or lateral leads is associated with an increased incidence of sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM), although the exact underlying mechanism is not known. As severe left ventricular hypertrophy and late gadolinium enhancement (LGE) are important risk factors for SCD in this population, we aimed to assess whether there was an association between an early repolarization pattern (ERP) and greater left ventricular mass (LVM) and LGE extent among patients with HCM.

METHODS

This was a retrospective cohort study of 85 consecutive patients with HCM who underwent cardiac magnetic resonance (CMR) and had an electrocardiogram without confounders (intraventricular conduction delay, complete left or right bundle branch block, or ventricular paced rhythm). Baseline characteristics and MRI-derived LVM and LGE extent were compared between patients with and without ERP.

RESULTS

ERP was present in 9 out of 85 patients (10.6%). Patients with ERP had greater indexed LVM compared to those without (112.5 ± 26.3 vs. 87.8 ± 24.6 g/m2, p = 0.006). Logistic regression analysis revealed a 4.2-fold increase in the odds of prevalent ERP per standard deviation increase in body surface area-indexed LVM (odds ratio 4.2; 95% CI 1.54-11.4, p = 0.005). There were no statistically significant differences regarding LGE extent between groups.

CONCLUSION

ERP is associated with greater CMR-derived LVM among patients with HCM. This finding could partially explain the association between J waves and a higher risk of SCD in this population. There were no differences in LGE extent. Further studies are needed to confirm this association and evaluate the importance of ERP as a marker of increased risk of SCD in HCM.

Low Left Atrial Strain Is Associated With Adverse Outcomes in Hypertrophic Cardiomyopathy Patients

BACKGROUND

Paroxysmal atrial fibrillation (PAF) and left atrial (LA) structural remodeling are common in hypertrophic cardiomyopathy (HCM) patients, who are also at risk for adverse cardiovascular outcomes.

OBJECTIVE

We assessed whether PAF and/or LA remodeling was associated with adverse outcomes in HCM.

METHODS

We retrospectively studied 45 HCM patients with PAF (PAF group) and 59 HCM patients without atrial fibrillation (AF; no-AF group). LA/left ventricular (LV) function and mechanics were assessed by echocardiography. Patients were followed for development of the composite endpoint comprising heart failure, stroke, and death.

RESULTS

Clinical/demographic characteristics, degree of LV hypertrophy, and E/e' were similar in the two groups The PAF group had significantly higher LA volume, but lower LA ejection fraction (LAEF), LA contractile, and reservoir strain/strain rate than the no-AF group. During follow-up, 27 patients developed the composite endpoint. Incidence of the composite endpoint was similar in the two groups. Absolute values of 23.8% for reservoir strain and 10.2% for conduit strain were the best cutoffs for the composite endpoint, using receiver operating characteristic analysis. Kaplan-Meier survival analysis showed lower event-free survival in patients with reservoir strain ≤23.8% or conduit strain ≤10.2%. Univariate Cox analysis revealed an association between female sex, LAEF, LA reservoir/conduit strain, and LV global longitudinal strain with the composite endpoint. The association between LA reservoir/conduit strain and the composite endpoint persisted after controlling for age, sex, LAEF, and LV global longitudinal strain.

CONCLUSIONS

In this pilot HCM patient study, PAF was associated with a greater degree of LA myopathy, and low LA reservoir and conduit strain were associated with higher risk for adverse cardiovascular outcomes.

Hypertrophic cardiomyopathy: a heart in need of an energy bar?

Hypertrophic cardiomyopathy (HCM) has been recently recognized as the most common inherited cardiovascular disorder, affecting 1 in 500 adults worldwide. HCM is characterized by myocyte hypertrophy resulting in thickening of the ventricular wall, myocyte disarray, interstitial and/or replacement fibrosis, decreased ventricular cavity volume and diastolic dysfunction. HCM is also the most common cause of sudden death in the young. A large proportion of patients diagnosed with HCM have mutations in sarcomeric proteins. However, it is unclear how these mutations lead to the cardiac phenotype, which is variable even in patients carrying the same causal mutation. Abnormalities in calcium cycling, oxidative stress, mitochondrial dysfunction and energetic deficiency have been described constituting the basis of therapies in experimental models of HCM and HCM patients. This review focuses on evidence supporting the role of cellular metabolism and mitochondria in HCM.