Ventricular Arrhythmia in Cancer Patients: Mechanisms, Treatment Strategies and Future Avenues

Cardiovascular disease and cancer are the leading causes of morbidity and mortality in the US. Despite the significant progress made in cancer treatment leading to improved prognosis and survival, ventricular arrhythmias (VA) remain a known cardiovascular complication either exacerbated or induced by the direct and indirect effects of both traditional and novel cancer treatments. Although interruption of cancer treatment because of VA is rarely required, knowledge surrounding this issue is essential for optimising the overall care of patients with cancer. The mechanisms of cancer-therapeutic-induced VA are poorly understood. This review will discuss the ventricular conduction (QRS) and repolarisation abnormalities (QTc prolongation), and VAs associated with cancer therapies, as well as existing strategies for the identification, prevention and management of cancer-treatment-induced VAs.

Association between corrected QT interval and long-term cardiovascular outcomes in elderly patients who had undergone endovascular therapy for lower extremity arterial disease

Background

Population-based studies have reported the association between prolonged corrected QT (QTc) intervals and an increased risk of adverse cardiovascular events. Data regarding the association between longer QTc intervals and incident cardiovascular outcomes in patients with lower extremity arterial disease (LEAD) are scarce.

Objective

To examine the impact of QTc interval on long-term cardiovascular outcomes in elderly patients with symptomatic LEAD.

Methods

This cohort study extracted data from the Tzu-chi Registry of ENDovascular Intervention for Peripheral Artery Disease (TRENDPAD) and enrolled 504 patients aged ≥ 70 treated with endovascular therapy for atherosclerotic LEAD from July 1, 2005, to December 31, 2019. The main outcomes of interest were all-cause mortality and major adverse cardiovascular events (MACE). Multivariate analysis was conducted using the Cox proportional hazard model to determine independent variables. We performed interaction analysis between corrected QT and other covariates and Kaplan-Meier analysis to compare the outcome of interest among the groups stratified by the tercile of QTc intervals.

Results

A total of 504 patients [235 men (46.6%); mean age, 79.9 ± 6.2 years; mean QTc interval, 459 ± 33 msec] entered the final data analysis. We categorized the baseline patient characteristics according to terciles of QTc intervals. During the median follow-up time of 3.15 (interquartile ranges, 1.65-5.42) years, we noted 264 deaths and 145 MACEs. The 5-year rates of freedom from all-cause mortality (71% vs. 57% vs. 31%, P < 0.001) and MACEs (83% vs. 67% vs. 46%, P < 0.001) were significantly different among the tercile groups. Multivariate analysis showed that a 1-SD increase in the QTc interval increased the risk of all-cause mortality [hazard ratio (HR) 1.49, P < 0.001] and MACEs (HR 1.59, P < 0.001) after adjusting for other covariates. The interaction analysis showed that QTc interval and C-reactive protein levels were most strongly associated with death (HR = 4.88, 95% CI 3.09-7.73, interaction P < 0.001) and MACEs (HR = 7.83, 95% CI 4.14-14.79, interaction P < 0.001).

Conclusions

In elderly patients with symptomatic atherosclerotic LEAD, a prolonged QTc interval is associated with advanced limb ischemia, multiple medical comorbidities, increased risk of MACEs, and all-cause mortality.

Development of an AI-Driven QT Correction Algorithm for Patients in Atrial Fibrillation

BACKGROUND

Prolongation of the QTc interval is associated with the risk of torsades de pointes. Determination of the QTc interval is therefore of critical importance. There is no reliable method for measuring or correcting the QT interval in atrial fibrillation (AF).

OBJECTIVES

The authors sought to evaluate the use of a convolutional neural network (CNN) applied to AF electrocardiograms (ECGs) for accurately estimating the QTc interval and ruling out prolongation of the QTc interval.

METHODS

The authors identified patients with a 12-lead ECG in AF within 10 days of a sinus ECG, with similar (±10 ms) QRS durations, between October 23, 2001, and November 5, 2021. A multilayered deep CNN was implemented in TensorFlow 2.5 (Google) to predict the MUSE (GE Healthcare) software-generated sinus QTc value from an AF ECG waveform, demographic characteristics, and software-generated features.

RESULTS

The study identified 6,432 patients (44% female) with an average age of 71 years. The CNN predicted sinus QTc values with a mean absolute error of 22.2 ms and root mean squared error of 30.6 ms, similar to the intrinsic variability of the sinus QTc interval. Approximately 84% and 97% of the model's predictions were contained within 1 SD (±30.6 ms) and 2 SD (±61.2 ms) from the sinus QTc interval. The model outperformed the AFQTc method, exhibiting narrower error ranges (mean absolute error comparison P < 0.0001). The model performed best for ruling out QTc prolongation (negative predictive value 0.82 male, 0.92 female; specificity 0.92 male, 0.97 female).

CONCLUSIONS

A CNN model applied to AF ECGs accurately predicted the sinus QTc interval, outperforming current alternatives and exhibiting a high negative predictive value.

Hospital-Based Quasi-Experimental Study on Hydroxychloroquine Pre-Exposure Prophylaxis for COVID-19 in Healthcare Providers with Its Potential Side-Effects

Considering that it has been more than 24 months since SARS-CoV-2 emerged, it is crucial to identify measures that prevent and control pathogen transmission in workplace settings. Our aim was to report results of a hospital-based program that delivered hydroxychloroquine (HCQ) tablets as COVID-19 prophylaxis to the frontline healthcare workers (HCW)s who cared for COVID-19 patients and to evaluate the efficacy of HCQ. Setting and participants: Quasi-experimental, controlled, single-center study. The included participants were doctors, nurses, health workers, cleaning staff, and non-healthcare supportive staff. The main outcome was contracting COVID-19 anytime during the period of taking the prophylaxis, confirmed by RT-PCR. A total of 336 participants, without any clinical evidence of COVID-19 and without any known contact with family members, were included in the trial; 230 were assigned to HCQ and 106 declined to take any drug. Results: Among the participants, 43 (18.7%) in the HCQ group and 11 (10.4%) participants in the control group developed COVID-19. For the evaluation of side effects, we evaluated 12-lead ECGs of both groups at the baseline and after 4 weeks to monitor QTc interval. A total of 91% (198 of 217) participants in the prophylaxis group and 92% (11 of 12) in the control group had a QTc < 45o msec, which is within normal limits. Conclusions: Although the number of symptomatic infections in health personnel was lower in the control group, the difference was not statistically significant. However, in the absence of any effective pre-exposure prophylaxis medicine for COVID-19, practicing proper infection prevention and control (IPC) and vaccination is the only way forward.

Serum High-sensitivity C-reactive Protein Level and Corrected QT Interval in Agricultural Workers in Myanmar Exposed to Chronic Occupational Organophosphate Pesticides

Although acute organophosphate (OP) pesticide poisoning is associated with the risk cardiovascular diseases (CVD), the association between chronic occupational OP pesticide exposure and CVD risk is limited. We investigated serum high-sensitivity C-reactive protein (hs-CRP) levels and QTc intervals in 45 agricultural workers who were chronically exposed to OP pesticides and 45 non-exposed subjects. Serum hs-CRP level was determined by enzyme-linked immunosorbent assay (ELISA) and a level >1.0 mg/l was regarded as CVD risk. The QT interval was measured by routine 12-lead Electrocardiogram (ECG) with Lead II rhythm, and QTc was calculated. The median value of the serum hs-CRP level [1.20 (0.67-2.38) vs 0.74 (0.41-1.17) mg/l, P <0.05] and the mean QTc interval (422.71 ± 23.73 vs 396.27 ± 18.48 ms, P <0.0001) was significantly higher in the OP pesticide exposed subjects. Pesticide exposure was significantly associated with CVD risk (Chi-Square χ² = 6.480, P = 0.011) and QTc interval prolongation (χ² = 13.846, P <0.001). A higher risk of CVD (odds ratio = 3.030; 95% confidence interval = 1.276 - 7.197) was observed in the OP pesticide exposed subjects. This study suggested that OP pesticide exposure should be considered as one of the significant risk factors for CVDs.

QT correction using Bazett's formula remains preferable in long QT syndrome type 1 and 2

Background

The heart rate (HR) corrected QT interval (QTc) is crucial for diagnosis and risk stratification in the long QT syndrome (LQTS). Although its use has been questioned in some contexts, Bazett's formula has been applied in most diagnostic and prognostic studies in LQTS patients. However, studies on which formula eliminates the inverse relation between QT and HR are lacking in LQTS patients.

We therefore determined which QT correction formula is most appropriate in LQTS patients including the effect of beta blocker therapy and an evaluation of the agreement of the formulae when applying specific QTc limits for diagnostic and prognostic purposes.

Methods

Automated measurements from routine 12‐lead ECGs from 200 genetically confirmed LQTS patients from two Swedish regions were included (167 LQT1, 33 LQT2). QT correction was performed using the Bazett, Framingham, Fridericia, and Hodges formulae. Linear regression was used to compare the formulae in all patients, and before and after the initiation of beta blocking therapy in a subgroup (n = 44). Concordance analysis was performed for QTc ≥ 480 ms (diagnosis) and ≥500 ms (prognosis).

Results

The median age was 32 years (range 0.1–78), 123 (62%) were female and 52 (26%) were children ≤16 years. Bazett's formula was the only method resulting in a QTc without relation with HR. Initiation of beta blocking therapy did not alter the result. Concordance analyses showed clinically significant differences (Cohen's kappa 0.629–0.469) for diagnosis and prognosis in individual patients.

Conclusion

Bazett's formula remains preferable for diagnosis and prognosis in LQT1 and 2 patients.

Magnetocardiographic identification of prolonged fetal corrected QT interval in women receiving treatment for opioid use disorder

AIM

Pregnant women undergoing treatment for opioid use disorder (OUD) may be exposed to multiple QT prolonging agents. We used magnetocardiography to measure fetal QT intervals in mothers with OUD on buprenorphine therapy.

METHODS

Fetal and maternal magnetocardiography was performed in pregnant women receiving buprenorphine-assisted treatment (Disorder group); these were matched by gestational age to pregnant women who were opiate naïve (Reference group). Corrected QT intervals were determined using Bazett's formula and compared between groups.

RESULTS

A total of eight women in the Disorder group matched to eight in the Reference group. Seven of the mothers (88%) in the Disorder group were smokers; there were no smokers in the Reference group. The average fetal corrected QT was significantly longer (P = 0.022) in the Disorder group than that in the Reference group (505 milliseconds [ms] ± 68.6 [standard deviation] vs 383 ms ± 70.3 [standard deviation]).

CONCLUSION

Novel data from this small sample demonstrate prolongation of fetal corrected QT in women with OUD participating in buprenorphine assisted therapy. Additional investigation from a larger sample is needed to clarify if fetal buprenorphine and/or tobacco exposure is associated with changes in fetal QT which would warrant further prenatal and postnatal testing.

Elective lung resection increases spatial QRS-T angle and QTc interval

BACKGROUND

Lung resection changes intra-thoracic anatomy, which may affect electrocardiographic results. While postoperative cardiac arrhythmias have been recognized after lung resection, no study has documented changes in vectorcardiographic variables in patients undergoing this surgery. The purpose of this study was to analyse changes in spatial QRS-T angle (spQRS-T) and corrected QT interval (QTc) after lung resection.

METHODS

Adult patients undergoing elective lung resection under general anaesthesia were studied. The patients were allocated into four groups: those undergoing (1) left lobectomy (LL); (2) left pneumonectomy (LP); (3) right lobectomy (RL); and (4) right pneumonectomy (RP). The spQRS-T angle and QTc interval were measured one day before surgery (baseline) and 24, 48 and 72 h after surgery.

RESULTS

Seventy-one adult patients (47 men and 24 women) aged 47-80 (65 ± 7) years were studied. In the study group as a whole, lung resection was associated with significant increases in spQRS-T (p < 0.001) and QTc (p < 0.05 at 24 and 48 h and p < 0.01 at 72 h). The greatest changes were noted in patients undergoing LP. Postoperative atrial fibrillation (AF) was noted in 6.4% of patients studied, in whom the widest spQRS-T angle and the most prolonged QTc intervals were also noted.

CONCLUSIONS

Lung resection widens the spQRS-T angle and prolongs the QTc interval, especially in patients undergoing LP. While postoperative AF was a relatively rare complication after lung resection in this study, it was associated with the widest spQRS-T angles and most prolonged QTc intervals.

Serum albumin level and abnormal corrected QT interval in patients with coronary artery disease and chronic kidney disease

BACKGROUND

Lower concentrations of serum albumin appear to be associated with an increased risk of all-cause and cardiovascular mortality, coronary heart disease, heart failure and stroke. However, little is known about the relationship between serum albumin level and prolonged QT interval.

AIM

To investigate whether lower serum albumin is associated with prolonged QT interval by recording 12-lead electrocardiography in patients with coronary artery disease and chronic kidney disease.

METHODS

This study included 1383 consecutive patients with coronary artery disease and chronic kidney disease (841 with acute coronary syndrome and 542 with elective percutaneous coronary intervention patients) who were enrolled in a disease management programme. Twelve-lead electrocardiography was recorded in each subject. We assessed the relationship between albumin levels (both as a continuous variable and stratified by tertile) at admission and corrected QT (QTc) prolongation.

RESULTS

Patients with abnormal QTc interval had lower serum albumin levels than those with normal and borderline QTc intervals. Statistically significant negative associations were observed between serum albumin levels and QTc interval (β = -0.211, P < 0.0001). Using multivariate and trend analyses, a lower concentration of serum albumin was independently associated with QTc prolongation in both the patients with acute coronary syndrome and elective percutaneous coronary intervention patients.

CONCLUSION

Concentrations of serum albumin were significantly lower in the patients with an abnormal QTc interval and were associated with QTc prolongation. Further studies are needed to clarify whether lower serum albumin plays a role in the pathogenesis of QTc prolongation.

Maximum QTc on Holter electrocardiography in children

BACKGROUND

Corrected QT interval (QTc) on electrocardiography (ECG) at rest and after exercise in a short daytime recording period may be insufficient for the diagnosis and management of long QT syndrome (LQTS), especially for LQTS type 2 and 3. Therefore, examination of QTc on Holter ECG is important. We designed a method of analyzing QTc on Holter ECG that can be performed in daily clinical practice by combining automatic and manual measurements.

METHODS

We reviewed the charts of healthy children (n = 210) and LQTS patients (n = 35) aged <16 years and analyzed QTc at rest and after exercise, and the maximum QTc on Holter ECG.

RESULTS

The QTc (Fridericia's correction) of most controls and LQTS patients reached the maximum at night or early in the morning. QTc differed according to sex and age. In the control group, QTc on ECG of all three types tended to lengthen with age. QTc after exercise was slightly longer than QTc at rest, and the maximum QTc on Holter ECG was much longer than both, reaching >450 ms in boys and 500 ms in girls. In most LQTS type 1 patients, QTc after exercise and that on Holter ECG tended to be long. In most LQTS type 2 and 3 patients, QTc at rest and that after exercise was long, and that on Holter ECG tended to be much longer.

CONCLUSIONS

The present method of analyzing QTc on Holter ECG, in which automatic and manual measurements are combined, is practical and may be useful for diagnosis and risk stratification of LQTS.

Arrhythmias and Electrocardiographic Changes in Systolic Heart Failure

Background:

Heart failure is a common condition that that leads to hospitalization. It is associated with various atrial and ventricular arrhythmias.

Aim:

The aim of this study is to find common arrhythmias and electrocardiographic changes in hospitalized patients who have systolic heart failure.

Materials and Methods:

This is a retrospective study of medical records, and electrocardiograms (EKGs) of 157 patients admitted to our hospital who had systolic heart failure with ejection fraction (EF) <50% on echocardiogram. Based on EF, the patients were divided into two groups; one with EF ≤ 35% and the other with EF > 35%. Twelve-lead EKG of these patients was studied to identify common arrhythmia and demographic variables; laboratory results were compared to identify the differences.

Results:

A total of 157 patients with systolic heart failure, 63.7% had an EF ≤ 35%. Hypertension 82.8%, diabetes 49%, coronary artery disease 40.8%, chronic obstructive pulmonary disease or bronchial asthma 22.3%, and stroke 12.1% were common associated co-morbidities. On analysis of EKG, 28.6% had tachycardia, 21.9% had prolonged PR > 200 ms, 16.3% had wide QRS > 120 ms, 70.7% had prolonged corrected QT (QTc), and 42.2% had left axis deviation. The most common arrhythmias were sinus tachycardia and atrial fibrillation/flutter which were found in 14.6% and 13.4%, respectively. The left ventricular hypertrophy was a common abnormality found in 22.4% followed by ventricular premature contractions 18.4%, atrial premature contractions 9.5%, and left bundle branch block 6.1%. Patients with severe systolic heart failure had prolonged QRS (P = 0.02) and prolonged QTc (P = 0.01) as compared to the other group.

Conclusions:

Sinus tachycardia and atrial fibrillation/flutter were common arrhythmias in patients with systolic heart failure. Patients with severe systolic heart failure had statistically significant prolongation of the QRS duration and QTc interval.

Small doses of droperidol do not present relevant torsadogenic actions: a double-blind, ondansetron-controlled study

AIM

Drugs used for postoperative nausea and vomiting prophylaxis are believed to provoke torsadogenic changes in cardiac repolarization. The aim of this study was to assess the effect of small doses of droperidol on the parameters of cardiac repolarization, including the QTc interval and transmural dispersion of repolarization.

METHODS

A total of 75 patients were randomly allocated to receive 0.625 or 1.25 mg droperidol or 8 mg ondansetron. The QTc interval was calculated using Bazett's formula and the Framingham correction. The transmural dispersion of repolarization was determined as Tpeak -Tend time.

RESULTS

Transient QT prolongation, corrected with both formulae, followed 1.25 mg of droperidol 10 min after administration. No change in the QTc value was observed in the other groups. When corrected with Bazett's formula, QTc was prolonged above 480 ms in two patients receiving 1.25 mg droperidol (at the 10(th) and 20(th) minute of the study) and in one receiving ondansetron. No patients developed a QTc B prolongation over 500 ms. No increase above 480 ms was observed relative to the Framingham correction method. There were no significant differences in the Tpeak -Tend time either between or within the groups.

CONCLUSION

In men without cardiovascular disorders small doses (1.25 mg) of droperidol prophylaxis induced transient QTc prolongation without changes in transmural dispersion of repolarization. The apparently low risk of the drug applies only in low risk male patients with a low pro-QTc score.

Evolution of clinical diagnosis in patients presenting with unexplained cardiac arrest or syncope due to polymorphic ventricular tachycardia

BACKGROUND

A systematic evaluation of patients with unexplained cardiac arrest (UCA) yields a diagnosis in 50% of the cases. However, evolution of clinical phenotype, identification of new disease-causing mutations, and description of new syndromes may revise the diagnosis.

OBJECTIVE

To assess the evolution in diagnosis among patients with initially UCA.

METHODS

Diagnoses were reviewed for all patients with UCA recruited from the Cardiac Arrest Survivors with Preserved Ejection Fraction Registry with at least 1 year of follow-up.

RESULTS

After comprehensive investigation of 68 patients (age 45.2 ± 14.9 years; 63% men), the initial diagnosis was as follows: idiopathic ventricular fibrillation (n = 34 [50%]), a primary arrhythmic disorder (n = 21 [31%]), and an occult structural cause (n = 13 [19%]). Patients were followed for 30 ± 17 months, during which time the diagnosis changed in 12 (18%) patients. A specific diagnosis emerged for 7 patients (21%) with an initial diagnosis of idiopathic ventricular fibrillation. A structural cardiomyopathy evolved in 2 patients with an initial diagnosis of primary electrical disorder, while the specific structural cardiomyopathy was revised for 1 patient. Two patients with an initial diagnosis of a primary arrhythmic disorder were subsequently considered to have a different primary arrhythmic disorder. A follow-up resting electrocardiogram was the test that most frequently changed the diagnosis (67% of the cases), followed by genetic testing (17%).

CONCLUSIONS

The reevaluation of patients presenting with UCA may lead to a change in diagnosis in up to 20%. This emphasizes the need to actively monitor the phenotype and also has implications for the treatment of these patients and the screening of their relatives.

A novel KCNQ1 missense mutation identified in a patient with juvenile-onset atrial fibrillation causes constitutively open IKs channels

BACKGROUND

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias. In some patients, the disease is inheritable; however, hereditary aspects of AF remain not fully elucidated.

OBJECTIVE

The purpose of this study was to identify genetic backgrounds that contribute to juvenile-onset AF and to define the mechanism.

METHODS

In 30 consecutive juvenile-onset AF patients (onset age <50 years), we screened AF-related genes (KCNQ1, KCNH2, KCNE1-3, KCNE5, KCNJ2, SCN5A). We analyzed the function of mutant channels using whole-cell patch-clamp techniques and computer simulations.

RESULTS

Among the juvenile-onset AF patients, we identified three mutations (10%): SCN5A-M1875T, KCNJ2-M301K, and KCNQ1-G229D. Because KCNQ1 variant (G229D) identified in a 16-year-old boy was novel, we focused on the proband. The G229D-IKs was found to induce a large instantaneous activating component without deactivation after repolarization to -50 mV. In addition, wild-type (WT)/G229D-IKs (WT and mutant coexpression) displayed both instantaneous and time-dependent activating currents. Compared to WT-IKs, the tail current densities in WT/G229D-IKs were larger at test potentials between -130 and -40 mV but smaller at test potentials between 20 and 50 mV. Moreover, WT/G229D-IKs resulted in a negative voltage shift for current activation (-35.2 mV) and slower deactivation. WT/G229D-IKs conducted a large outward current induced by an atrial action potential waveform, and computer simulation incorporating the WT/G229D-IKs results revealed that the mutation shortened atrial but not ventricular action potential.

CONCLUSION

A novel KCNQ1-G229D mutation identified in a juvenile-onset AF patient altered the IKs activity and kinetics, thereby increasing the arrhythmogenicity to AF.

The QT interval and risk of incident atrial fibrillation

BACKGROUND

Abnormal atrial repolarization is important in the development of atrial fibrillation (AF), but no direct measurement is available in clinical medicine.

OBJECTIVE

To determine whether the QT interval, a marker of ventricular repolarization, could be used to predict incident AF.

METHODS

We examined a prolonged QT interval corrected by using the Framingham formula (QT(Fram)) as a predictor of incident AF in the Atherosclerosis Risk in Communities (ARIC) study. The Cardiovascular Health Study (CHS) and Health, Aging, and Body Composition (ABC) study were used for validation. Secondary predictors included QT duration as a continuous variable, a short QT interval, and QT intervals corrected by using other formulas.

RESULTS

Among 14,538 ARIC study participants, a prolonged QT(Fram) predicted a roughly 2-fold increased risk of AF (hazard ratio [HR] 2.05; 95% confidence interval [CI] 1.42-2.96; P < .001). No substantive attenuation was observed after adjustment for age, race, sex, study center, body mass index, hypertension, diabetes, coronary disease, and heart failure. The findings were validated in Cardiovascular Health Study and Health, Aging, and Body Composition study and were similar across various QT correction methods. Also in the ARIC study, each 10-ms increase in QT(Fram) was associated with an increased unadjusted (HR 1.14; 95% CI 1.10-1.17; P < .001) and adjusted (HR 1.11; 95% CI 1.07-1.14; P < .001) risk of AF. Findings regarding a short QT interval were inconsistent across cohorts.

CONCLUSIONS

A prolonged QT interval is associated with an increased risk of incident AF.

The phenotype characteristics of type 13 long QT syndrome with mutation in KCNJ5 (Kir3.4-G387R)

BACKGROUND

Long QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in the KCNJ5-encoded cardiac G-protein-coupled inward rectifier potassium channel subtype 4 protein. The electrocardiographic (ECG) features of LQT13 are not described yet.

OBJECTIVE

To describe for the first time in detail the phenotype-genotype relationship of the ECG and clinical features in patients with LQT13.

METHODS

The 12-lead ECGs, 24-hour Holter recordings, and clinical information from KCNJ5-G387R mutation carriers of a fourth-generation Han Chinese family with LQT13 and a group of healthy Chinese individuals were analyzed.

RESULTS

Compared with the analysis of the healthy group (n = 8), age- and sex-matched pair analysis revealed that the mutation carriers (n = 8) had ventricular repolarization abnormality results in the prolongation of corrected QT and QTpeak intervals (P < .01); greater combined measure of repolarization morphology (T-wave morphology combination score) based on asymmetry, flatness, and notch (P < .01); and reduced low frequency/high frequency ratio of heart rate variability (P < .01) as a reflection of cardiac autonomic imbalance. Mean heart rate, time domain parameters of heart rate variability, time interval from T-wave peak to T-wave end, and T-wave amplitude were similar.

CONCLUSIONS

This study demonstrates for the first time the ECG features of patients with LQT13. Our data suggest that QTpeak intervals and T-wave morphology combination score may be the better parameters than the corrected QT interval to predict the phenotype-genotype relationship in patients with LQT13.

Prolonged Corrected QT Interval in Patients with Myotonic Dystrophy Type 1

BACKGROUND AND PURPOSE

Sudden cardiac death is one of the leading causes of death in patients with myotonic dystrophy type 1 (DM1). It has been proposed that a prolonged QT interval is associated with sudden cardiac death in several neurological diseases, including multiple system atrophy, idiopathic Parkinson's disease, and diabetic autonomic neuropathy. However, analyses of the corrected QT (QTc) interval in DM1 patients are rare in the literature. The purposes of this study were to determine the association between the QT interval and DM1, and the affecting factors.

METHODS

Thirty-nine patients diagnosed with DM1 through genetic testing were enrolled. The QTc interval (calculated using Bazett's formula: QTc=QT/√RR) was compared between these patients and 39 normal healthy controls. The clinical and laboratory factors affecting QTc interval in the patient group were investigated.

RESULTS

The QTc interval was significantly longer in the DM1 group (411.2±44.7 msec, mean±SD) than in the normal control group (355.6±20.6 msec). Intragroup analysis revealed that a prolonged QTc interval in DM1 patients was associated with being female and older, having a longer disease duration, and exhibiting abnormal electrocardiography findings.

CONCLUSIONS

The higher incidence of sudden cardiac death in the DM1 population is associated with the observed prolonged QTc interval in those patients.

Magnetophysiologic and echocardiographic comparison of blocked atrial bigeminy and 2:1 atrioventricular block in the fetus

BACKGROUND

Blocked atrial bigeminy (BAB) and second-degree atrioventricular block with 2:1 conduction block (2:1 AVB) both present as ventricular bradycardia and can be difficult to distinguish by echocardiography. Since the prognosis and clinical management of these rhythms are different, an accurate diagnosis is essential.

OBJECTIVE

To identify magnetic and mechanical heart rate and rhythm parameters that could reliably distinguish BAB from 2:1 AVB.

METHODS

A retrospective study of ten BAB and seven 2:1 AVB subjects was performed, using fMCG and pulsed Doppler ultrasound.

RESULTS

Distinguishing BAB from 2:1 AVB by using fMCG was relatively straightforward because in BAB the ectopic P wave (P') occurred early, resulting in a bigeminal (short-long) atrial rhythm. The normalized coupling interval of the ectopic beat (PP' of the blocked beat to PP of the conducted beat) was 0.29 ± 0.03. In contrast, the echocardiographic assessment of inflow-outflow gave a normalized mechanical coupling interval (AA'/AA) near 0.5, which made it difficult to distinguish BAB from 2:1 AVB. Heart rate distinguished most subjects with BAB from those with 2:1 AVB (82 ± 5.7 beats/min vs 69 ± 4.2 beats/min), but was not a completely reliable indicator. In most subjects, BAB alternated with sinus rhythm or other rhythms, resulting in complex heart rate and rhythm patterns.

CONCLUSIONS

Fetal BAB and 2:1 AV block can be difficult to distinguish using echocardiography because in many fetuses with BAB the mechanical rhythm does not accurately reflect the magnetic rhythm. fMCG provides a more reliable means of making a differential diagnosis.

A public-private consortium advances cardiac safety evaluation: achievements of the HESI Cardiac Safety Technical Committee

INTRODUCTION

The evaluation of cardiovascular side-effects is a critical element in the development of all new drugs and chemicals. Cardiac safety issues are a major cause of attrition and withdrawal due to adverse drug reactions (ADRs) in pharmaceutical drug development.

METHODS

The evolution of the HESI Technical Committee on Cardiac Safety from 2000-2013 is presented as an example of an effective international consortium of academic, government, and industry scientists working to improve cardiac safety.

RESULTS AND DISCUSSION

The HESI Technical Committee Working Groups facilitated the development of a variety of platforms for resource sharing and communication among experts that led to innovative strategies for improved drug safety. The positive impacts arising from these Working Groups are described in this article.