The prevalence and the prognostic value of microvolt T-wave alternans in patients with hypertrophic cardiomyopathy

Deceleration and acceleration capacities of heart rate in patients with hypertrophic cardiomyopathy: results of a five-year prospective study

Aim. To study the features of deceleration capacity (DC) and acceleration capacity (AC) in patients with hypertrophic cardiomyopathy (HCM) and assess the correlation of these indicators with known complications and risk factors for sudden cardiac death (SCD).

Material and methods. A total of 50 patients with HCM were examined. Comparable by sex and age, the control group included 50 individuals without cardiovascular diseases. All patients underwent 24-hour electrocardiographic monitoring with the determination of DC and AC. The follow-up period lasted 5 years. Lethal outcomes were recorded in 6%, including SCD — 4%.

Results. Patients with HCM were characterized by significantly lower mean DC — 5,5 [3,7; 7,4] vs 7,8 [7,1; 8,5] ms (p=0,0001) and significantly higher AC– -7,4 [-8,9; -5,8] vs -9,3 [-10,0; -8,6] ms (p=0,001) compared with the control group. In 36% of patients with HCM, pathological values of DC ≤4,5 ms were detected, while in all individuals in the control group, DC corresponded to a favorable prognosis (p=0,001). In patients with and without nonsustained ventricular tachycardia (NSVT), a decrease in DC was detected in 56% and 25,5% (p=0,043), respectively, while with and without heart failure (HF) — in 78% and 27% (p=0,016), respectively. In patients with HF (p=0,003) and paroxysmal atrial fibrillation (p=0,023), mean DC values were significantly lower than in patients without these complications. HF was an independent predictor of DC reduction. DC decrease was not associated with an increase in SCD risk estimated using the HCM Risk-SCD calculator.

Conclusion. Patients with HCM compared with healthy individuals are characterized by lower DC and higher AC values. Among patients with HCM, a decrease in DC is typical for patients with a more severe disease course (HF, AF, NSVT). However, the rationale for using this indicator in SCD risk stratification needs to be clarified.

Microvolt QRS Alternans in Hypertrophic Cardiomyopathy: A Novel Risk Marker of Late Ventricular Arrhythmias

Background

Unlike T‐wave alternans (TWA), the relation between QRS alternans (QRSA) and ventricular arrhythmia (VA) risk has not been evaluated in hypertrophic cardiomyopathy (HCM). We assessed microvolt QRSA/TWA in relation to HCM risk factors and late VA outcomes in HCM.

Methods and Results

Prospectively enrolled patients with HCM (n=130) with prophylactic implantable cardioverter‐defibrillators underwent digital 12‐lead ECG recordings during ventricular pacing (100–120 beats/min). QRSA/TWA was quantified using the spectral method. Patients were categorized as QRSA+ and/or TWA+ if sustained alternans was present in ≥2 precordial leads. The VA end point was appropriate implantable cardioverter‐defibrillator therapy over 5 years of follow‐up. QRSA+ and TWA+ occurred together in 28% of patients and alone in 7% and 7% of patients, respectively. QRSA magnitude increased with pacing rate (1.9±0.6 versus 6.2±2.0 µV; P=0.006). Left ventricular thickness was greater in QRSA+ than in QRSA− patients (22±7 versus 20±6 mm; P=0.035). Over 5 years follow‐up, 17% of patients had VA. The annual VA rate was greater in QRSA+ versus QRSA− patients (5.8% versus 2.0%; P=0.006), with the QRSA+/TWA− subgroup having the greatest rate (13.3% versus 2.6%; P<0.001). In those with <2 risk factors, QRSA− patients had a low annual VA rate compared QRSA+ patients (0.58% versus 7.1%; P=0.001). Separate Cox models revealed QRSA+ (hazard ratio [HR], 2.9 [95% CI, 1.2–7.0]; P=0.019) and QRSA+/TWA− (HR, 7.9 [95% CI, 2.9–21.7]; P<0.001) as the most significant VA predictors. TWA and HCM risk factors did not predict VA.

Conclusions

In HCM, microvolt QRSA is a novel, rate‐dependent phenomenon that can exist without TWA and is associated with greater left ventricular thickness. QRSA increases VA risk 3‐fold in all patients, whereas the absence of QRSA confers low VA risk in patients with <2 risk factors.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02560844.

Follow-up and prognosis of HCM

[first paragraph of article]The frequency of follow-up visits in hypertrophic cardiomyopathy (HCM) patients is mainly determined by their symptoms, age and severity of disease. Clinical visits should focus on sudden cardiac death (SCD) and embolic risk-assessment, changes in symptoms, cardiac rhythm, left ventricular outflow tract obstruction (LVOTO) and left ventricular (LV) systolic function.

Exercise-induced quantitative microvolt T-wave alternans in hypertrophic cardiomyopathy

BACKGROUND/PURPOSE

Patients with hypertrophic cardiomyopathy (HCM) have elevated risk for sudden cardiac death (SCD). Our study aimed to quantitatively characterize microvolt T-wave alternans (TWA), a potential arrhythmia risk stratification tool, in this HCM patient population.

METHODS

TWA was analyzed with the quantitative modified moving average (MMA) in 132 HCM patients undergoing treadmill exercise testing, grouped according to Maron score risk factors as high-risk (H-Risk, n=67,), or low-risk (L-Risk, n=65, without these risk factors).

RESULTS

TWA levels were much higher for the H-Risk than for the L-Risk group (101.40±75.61 vs. 54.35±46.26μV; p<0.0001). A 53μV cut point, set by receiver operator characteristic (ROC), identified H-Risk patients (82% sensitivity, 69% specificity).

CONCLUSIONS

High TWA levels were found for hypertrophic cardiomyopathy patients. Abnormal TWA associated with major risk factors for SCD: non-sustained ventricular tachycardia on Holter (p=0.001), family history of SCD (p=0.006), septal thickness ≥30mm (p<0.001); and inadequate blood pressure response to effort (p=0.04).

Late gadolinium enhancement on cardiac magnetic resonance represents the depolarizing and repolarizing electrically damaged foci causing malignant ventricular arrhythmia in hypertrophic cardiomyopathy

BACKGROUND

The presence of a myocardial scar detected by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) has been described as a predictor of all-cause mortality in hypertrophic cardiomyopathy (HCM). However, the detailed spatial relationship between LGE site and electrical abnormality is unclear in high-risk HCM with malignant arrhythmia.

OBJECTIVE

The purpose of this study was to elucidate the detailed relationship between the site on CMR imaging and the electrically damaged site, a potential origin of ventricular arrhythmias in patients with HCM.

METHODS

Fifty consecutive HCM patients underwent contrast-enhanced CMR. Of those patients, 18 patients with ventricular tachycardia underwent electrophysiology study including endocardial mapping of the left ventricle (LV). The LGE area was calculated at 12 different LV sites: anterior, lateral, posterior, and septal segments of the basal, middle, and apical portions. At each LV site, the bipolar electrogram, effective refractory period (ERP), and monophasic action potential were recorded.

RESULTS

LGE-positive segments demonstrated a significantly lower amplitude (4.0 ± 2.8 mV vs 7.3 ± 3.6 mV; P < .001), longer duration (54.7 ± 17.8 vs 40.6 ± 7.8 ms; P < .001), longer ERP (320 ± 42 ms vs 284 ± 37 ms; P = .001), and longer monophasic action potential duration measured at 90% repolarization (321 ± 19 ms vs 283 ± 25 ms; P < .001) than did LGE-negative segments. The LGE area negatively correlated with the amplitude (r = -0.59; P < .001) and positively correlated with the duration (r = 0.64; P < .001), ERP (r = 0.44; P < .001), and action potential duration measured at 90% repolarization (r = 0.63; P < .001). All the observed VTs originated from LGE-positive segments.

CONCLUSION

The spatial distribution of LGE significantly correlates with depolarizing and repolarizing electrical damage in high-risk HCM with malignant ventricular arrhythmia.