Subclinical Cardiomyopathy and Long QT Syndrome: An Echocardiographic Observation

Eosinophilic Infiltration of the Sino-Atrial Node in Sudden Cardiac Death Caused by Long QT Syndrome

Sudden death is defined as the unexpected death of a healthy person that occurs within the first hour of the onset of symptoms or within 24 h of the victim being last seen alive. In some of these cases, rare deleterious variants of genes associated with inherited cardiac disorders can provide a highly probable explanation for the fatal event. We report the case of a 21-year-old obese woman who lost consciousness suddenly in a public place and was pronounced dead after hospital admission. Clinical autopsy showed an inconclusive gross examination, while in the histopathological analysis an eosinophilic inflammatory focus and interstitial fibrosis in the sino-atrial node were found. Molecular autopsy revealed an intronic variant in the KCNQ1 gene (c.683 + 5G > A), classified as likely pathogenic for long QT syndrome according to the guidelines provided by the American College of Medical Genetics and Genomics. Therefore, there were many anomalies that could have played a role in the causation of the sudden death, such as the extreme obesity, the cardiac anomalies and the KNCQ1 variant. This case depicts the difficult interpretation of rare cardiac structural abnormalities in subjects carrying rare variants responsible for inherited arrhythmic disorders and the challenge for the forensic pathologist to make causal inferences in the determinism of the unexpected decease.

Long QT syndrome and left ventricular non-compaction in a family with KCNH2 mutation: A case report

BACKGROUND

Left ventricular non-compaction (LVNC) is an abnormality of the myocardium, characterized by prominent left ventricular trabeculae and deep inter-trabecular recesses. Long QT syndrome (LQTS) is a cardiac ion channelopathy presenting with a prolonged QT interval on resting electrocardiogram and is associated with increased susceptibility to sudden death. The association between LVNC and LQTS is uncommon.

CASE PRESENTATION

We report an Italian family with a novel pathogenic KCNH2 variant who presented with clinical features of LVNC and LQTS. The proband came to our attention after two syncopal episodes without prodromal symptoms. His ECG showed QTc prolongation and deep T wave inversion in anterior leads, and the echocardiogram fulfilled LVNC criteria. After that, also his sister was found to have LQTS and LVNC, while his father only presented LQTS.

CONCLUSIONS

Physicians should be aware of the possible association between LVNC and LQTS. Even if this association is rare, patients with LVNC should be investigated for LQTS to prevent possible severe or even life-threatening arrhythmic episodes.

Left Ventricular Contraction Duration Is the Most Powerful Predictor of Cardiac Events in LQTS: A Systematic Review and Meta-Analysis

Background: Long-QT syndrome (LQTS) is primarily an electrical disorder characterized by a prolonged myocardial action potential. The delay in cardiac repolarization leads to electromechanical (EM) abnormalities, which adds a diagnostic value for LQTS. Prolonged left ventricular (LV) contraction was identified as a potential risk for arrhythmia. The aim of this meta-analysis was to assess the best predictor of all EM parameters for cardiac events (CEs) in LQTS patients. Methods: We systematically searched all electronic databases up to March 2020, to select studies that assessed the relationship between echocardiographic indices—contraction duration (CD), mechanical dispersion (MD), QRS onset to peak systolic strain (QAoC), and the EM window (EMW); and electrical indices— corrected QT interval (QT_C), QT_C dispersion, RR interval in relation to CEs in LQTS. This meta-analysis included a total of 1041 patients and 373 controls recruited from 12 studies. Results: The meta-analysis showed that LQTS patients had electrical and mechanical abnormalities as compared to controls—QT_C, WMD 72.8; QT_C dispersion, WMD 31.7; RR interval, WMD 91.5; CD, WMD 49.2; MD, WMD 15.9; QAoC, WMD 27.8; and EMW, WMD −62.4. These mechanical abnormalities were more profound in symptomatic compared to asymptomatic patients in whom disturbances were already manifest, compared to controls. A CD ≥430 ms had a summary sensitivity (SS) of 71%, specificity of 84%, and diagnostic odds ratio (DOR) >19.5 in predicting CEs. EMW and QT_C had a lower accuracy. Conclusions: LQTS is associated with pronounced EM abnormalities, particularly prolonged LV myocardial CD, which is profound in symptomatic patients. These findings highlight the significant role of EM indices like CD in managing LQTS patients.

Prolonged left ventricular contraction duration in apical segments as a marker of arrhythmic risk in patients with long QT syndrome

AIMS

Long QT syndrome (LQTS) is an inherited cardiac ion channelopathy predisposing to life-threatening ventricular arrhythmias and sudden cardiac death. The aim of this study was to investigate left ventricular mechanical abnormalities in LQTS patients and establish a potential role of strain as a marker of arrhythmic risk.

METHODS AND RESULTS

We included 47 patients with genetically confirmed LQTS (22 LQT1, 20 LQT2, 3 LQT3, and 2 SCN3B) and 25 healthy controls. A history of cardiac events was present in 30 LQTS subjects. Tissue Doppler and speckle tracking echocardiography were performed and contraction duration was measured by radial and longitudinal strain. The radial strain characteristic was subdivided into two planes - the basal and the apical. Left ventricular ejection fraction and global longitudinal strain were normal in LQTS patients. Mean contraction duration was longer in LQTS patients compared with controls in regard to basal radial strain (491 ± 57 vs. 437 ± 55 ms, P < 0.001), apical radial strain (450 ± 53 vs. 407 ± 53 ms, P = 0.002), and longitudinal strain (445 ± 34 vs. 423 ± 43 ms, P = 0.02). Moreover, contraction duration obtained from apical radial strain analysis was longer in symptomatic compared with asymptomatic LQTS mutation carriers (462 ± 49 vs. 429 ± 55 ms, P = 0.024), as well as in subject with mutations other than LQT1 considered to be at higher risk (468 ± 50 vs. 429 ± 49 ms, P = 0.01).

CONCLUSION

Myocardial contraction duration is prolonged for both radial and longitudinal directions in LQTS patients. Regional left ventricular function analysis may contribute to risk stratification. Apical radial deformation seems to select subjects at higher risk of arrhythmic events.

Left Ventricular Isovolumetric Relaxation Time Is Prolonged in Fetal Long-QT Syndrome

BACKGROUND

Long-QT syndrome (LQTS), an inherited cardiac repolarization disorder, is an important cause of fetal and neonatal mortality. Detecting LQTS prenatally is challenging. A fetal heart rate (FHR) less than third percentile for gestational age is specific for LQTS, but the sensitivity is only ≈50%. Left ventricular isovolumetric relaxation time (LVIRT) was evaluated as a potential diagnostic marker for fetal LQTS.

METHODS AND RESULTS

LV isovolumetric contraction time, LV ejection time, LVIRT, cycle length, and FHR were measured using pulsed Doppler waveforms in fetuses. Time intervals were expressed as percentages of cycle length, and the LV myocardial performance index was calculated. Single measurements were stratified by gestational age and compared between LQTS fetuses and controls. Receiver-operator curves were performed for FHR and normalized LVIRT (N-LVIRT). A linear mixed-effect model including multiple measurements was used to analyze trends in FHR, N-LVIRT, and LV myocardial performance index. There were 33 LQTS fetuses and 469 controls included. In LQTS fetuses, the LVIRT was prolonged in all gestational age groups (P<0.001), as was the N-LVIRT. The best cutoff to diagnose LQTS was N-LVIRT ≥11.3 at ≤20 weeks (92% sensitivity, 70% specificity). Simultaneous analysis of N-LVIRT and FHR improved the sensitivity and specificity for LQTS (area under the curve=0.96; 95% confidence interval, 0.82-1.00 at 21-30 weeks). N-LVIRT, LV myocardial performance index, and FHR trends differed significantly between LQTS fetuses and controls through gestation.

CONCLUSIONS

The LVIRT is prolonged in LQTS fetuses. Findings of a prolonged N-LVIRT and sinus bradycardia can improve the prenatal detection of fetal LQTS.

Preparticipation Cardiovascular Screening of Student-Athletes with Echocardiography: Ethical, Clinical, Economic, and Legal Considerations

PURPOSE OF REVIEW

To identify whether the use of echocardiography is a viable approach for the screening of athletes for the prevention of sudden cardiac death when considering ethical, clinical, economic, and legal issues.

RECENT FINDINGS

Ethical musings, echocardiographic findings, economic calculations, and legal analysis suggest that echocardiographic screening may reduce sudden cardiac death on the athletic field. Ethical, clinical, economic, and legal considerations suggest echocardiographic screening is a viable option to meet the societal goal to prevent athletic field sudden death.

Exercise worsening of electromechanical disturbances: A predictor of arrhythmia in long QT syndrome

Background

Electromechanical (EM) coupling heterogeneity is significant in long QT syndrome (LQTS), particularly in symptomatic patients; EM window (EMW) has been proposed as an indicator of interaction and a better predictor of arrhythmia than QTc.

Hypothesis

To investigate the dynamic response of EMW to exercise in LQTS and its predictive value of arrhythmia.

Methods

Forty‐seven LQTS carriers (45 ± 15 years, 20 with arrhythmic events), and 35 controls underwent exercise echocardiogram. EMW was measured as the time difference between aortic valve closure on Doppler and the end of QT interval on the superimposed electrocardiogram (ECG). Measurements were obtained at rest, peak exercise (PE) and 4 minutes into recovery.

Results

Patients did not differ in age, gender, heart rate, or left ventricular ejection fraction but had a negative resting EMW compared with controls (−42 ± 22 vs 17 ± 5 ms, P < 0.0001). EMW became more negative at PE (−89 ± 43 vs 16 ± 7 ms, P = 0.0001) and recovery (−65 ± 39 vs 16 ± 6 ms, P = 0.001) in patients, particularly the symptomatic, but remained unchanged in controls. PE EMW was a stronger predictor of arrhythmic events than QTc (AUC:0.765 vs 0.569, P < 0.001). B‐blockers did not affect EMW at rest but was less negative at PE (BB: −66 ± 21 vs no‐BB: −113 ± 25 ms, P < 0.001). LQT1 patients had worse PE EMW negativity than LQT2.

Conclusion

LQTS patients have significantly negative EMW, which worsens with exercise. These changes are more pronounced in patients with documented arrhythmic events and decrease with B‐blocker therapy. Thus, EMW assessment during exercise may help improve risk stratification and management of LQTS patients.

The congenital long QT syndrome Type 3: An update

Congenital long QT syndrome type 3 (LQT3) is the third in frequency compared to the 15 forms known currently of congenital long QT syndrome (LQTS). Cardiac events are less frequent in LQT3 when compared with LQT1 and LQT2, but more likely to be lethal; the likelihood of dying during a cardiac event is 20% in families with an LQT3 mutation and 4% with either an LQT1 or an LQT2 mutation. LQT3 is consequence of mutation of gene SCN5A which codes for the Nav1.5 Na+ channel α-subunit and electrocardiographically characterized by a tendency to bradycardia related to age, prolonged QT/QTc interval (mean QTc value 478 ± 52 ms), accentuated QT dispersion consequence of prolonged ST segment, late onset of T wave and frequent prominent U wave because of longer repolarization of the M cell across left ventricular wall.

Risk stratification in patients with heart failure: the value of considering both global longitudinal left ventricular strain and mechanical dispersion

In previous studies, mechanical dispersion (MD) predicted ventricular arrhythmias independently of left ventricular ejection fraction (LVEF). Moreover, the combination of MD and global longitudinal strain (GLS) increased the prediction of arrhythmic events. We investigated the prognostic value of a new 2-dimensional strain index, GLS/MD, in patients with heart failure (HF). We analyzed 340 consecutive HF outpatients in sinus rhythm. Echocardiography was performed at 1.6 ± 0.4 months after hospital discharge. The end point included sudden cardiac death, ventricular fibrillation, and sustained ventricular tachycardia (SCD/VA). During the follow-up period (36 ± 9 months), SCD/VA occurred in 48 patients (14.1%). A multivariate Cox regression analysis, which included LVEF, early diastolic transmitral / mitral annular velocity ratio (E/E'), GLS, MD, and GLS/MD in the model, revealed that GLS/MD was the best independent predictor of SCD/VA (HR = 3.22, 95% confidence interval = 1.72-6.15, p = 0.03). Separate inclusion of LVEF, systolic mitral annular velocity, E/E', GLS, and MD together with GLS/MD showed that GLS/MD remained the best predictor of SCD/VA (each p < 0.05). The optimal GLS/MD cutoff value to predict SCA/VA was -0.20%/ms (80% sensitivity, 76% specificity). Irrespective of LVEF, free survival was significantly better in patients with GLS/MD ≤ -0.2%/ms (log-rank test, p < 0.001). In conclusion, GLS/MD may improve cardiovascular risk stratification in subjects with HF.

Vectorcardiography identifies patients with electrocardiographically concealed long QT syndrome

BACKGROUND

Long QT syndrome (LQTS) and genotypic subtypes are associated with distinctive T-wave patterns, arrhythmogenic triggers, and corrected QT (QTc) interval risk associations. Twenty percent of patients with LQTS have normal QTc values, defined as electrographically concealed LQTS (ecLQTS). Vectorcardiography (VCG) has value for sudden cardiac death risk assessment.

OBJECTIVE

The purpose of this study was to determine the use of VCG to identify patients with ecLQTS.

METHODS

We performed a retrospective analysis in patients with ecLQTS with resting QTc values <440 ms. Computerized derivation of the spatial mean and peak QRS-T angles, QTpeak, Tpeak-Tend (angle between QRS and T-wave peak amplitudes in 3-dimensional space), and T-wave eigenvalues (TwEVs; amplitudes [in microvolts] for each of the first 4 TwEVs were derived from the 12-lead electrocardiogram) was performed. The results were compared with those for healthy controls. Intergenotype differences were analyzed.

RESULTS

Of 610 patients with LQTS, 169 patients (28%) had ecLQTS (86 (51%) men; mean age 22 ± 16 years; mean QTc interval 422 ± 14 ms). There were 519 healthy controls (44% men; mean age 19.8 ± 13.8 years) with a mean QTc interval of 426 ± 28 ms. Among VCG parameters, QTpeak and TwEVs significantly differentiated patients with ecLQTS from controls (P ≤ .01 for each) as well as differentiated KCNQ1-encoded type 1 LQTS (ecLQT1), KCNH2-encoded type 2 LQTS (ecLQT2), and SCN5A-encoded type 3 LQTS (ecLQT3) from controls (P < .01). ecLQT3 was differentiated from controls and ecLQT1 and ecLQT2 by the fourth TwEV (P < .01 for each). The fourth TwEV differentiated symptomatic patients with ecLQTS from asymptomatic patients with ecLQTS (P < .01).

CONCLUSION

ecLQTS can be distinguished from controls using QTpeak. ecLQT3 was best differentiated by the fourth TwEV. VCG may facilitate familial diagnostic anticipation of LQTS status before the completion of mutation-specific genetic testing even with normal resting QTc values.

Cardiac Mechanical Alterations and Genotype Specific Differences in Subjects With Long QT Syndrome

OBJECTIVES

This study aimed to explore systolic and diastolic function and to investigate genotype-specific differences in subjects with long QT syndrome (LQTS).

BACKGROUND

LQTS is an arrhythmogenic cardiac ion channelopathy that traditionally has been considered a purely electrical disease. The most commonly affected ion channels are the slow potassium channel, IKs (KCNQ1 gene/LQT1), and the rapid potassium channel, IKr (KCNH2 gene/LQT2). Recent reports have indicated mechanical abnormalities in patients with LQTS.

METHODS

We included 192 subjects with genotyped LQTS (139 LQT1, 53 LQT2). Healthy persons of similar age and sex as patients served as controls (n = 60). Using echocardiography, we assessed systolic function by left ventricular (LV) ejection fraction (EF), global longitudinal strain (GLS), and contraction duration (16 LV segments). Mechanical dispersion was calculated as standard deviation of contraction duration. Time difference between contraction duration and QT interval from electrocardiography (ECG) was defined as electromechanical time difference. We assessed diastolic function by transmitral filling velocities, early diastolic myocardial velocity (e'), and left atrial volume index (LAVI). Heart rate corrected QT interval (QTc) was assessed from 12-lead ECG.

RESULTS

Systolic function by GLS was reduced in subjects with LQTS compared with healthy controls (-22.1 ± 2.1% vs. -23.0 ± 2.0%, p = 0.01), and GLS was worse in subjects with LQT2 compared with subjects with LQT1 (p = 0.01). Subjects with LQTS had longer contraction duration (426 ± 41 ms vs. 391 ± 36 ms, p < 0.001) and more dispersed contractions (33 ± 14 ms vs. 21 ± 7 ms, p < 0.001) compared with healthy controls. Diastolic function was also reduced in subjects with LQTS compared with healthy controls; e' was lower (10.7 ± 2.7 cm/s vs. 12.5 ± 2.0 cm/s, p < 0.001), and LAVI was increased (30 ± 8 ml/m(2) vs. 26 ± 5 ml/m(2), p = 0.01), also when adjusted for age and other possible confounders.

CONCLUSIONS

Subjects with LQTS had a consistent reduction in both systolic and diastolic function compared with healthy controls. Differences in myocardial function between subjects with LQT1 and subjects with LQT2 may indicate that mechanical alterations in LQTS are genotype specific.