Analysis of the Incidence and Clinical Significance of Long and Short Corrected QT Interval in Electrocardiogram in Healthy Population of Changsha in China

ABSTRACT Objective: To analyse the incidence of long and short corrected QT (QTc) in a healthy sample of the population of Changsha in China. Methods: Standard 12-lead electrocardiograms (ECGs) were performed on 4025 subjects in Changsha of China, whose age ranged from 6 minutes after birth to 83 years, between January 1993 and December 2012. Heart rate and QT interval were measured and recorded. Corrected QT was calculated with Bazett´s formula (QTc = QT/RR0.5). All recruited individuals had taken healthy examination, ruling out general health issue, in The Second Xiangya Hospital of Central South University. Statistical analyses were performed using the SPSS 16.0 software (IBM Corp, Armonk, NY, USA). Results: The incidence of short QTc was 7.13% (287/4025 cases). The peak values of the incidence were in the 30-40 years group (15.71%). The low values were in the 1-3 months group and 3-6 months group (0%, 0.76%), respectively. The incidence of long QTc was 3.16% (127/4025 cases). The values diminished significantly after adulthood. The low values were in the age groups of 18-30 years (0.86%) and 30-40 years (0.71%), respectively. After the age of 50 years, the incidence of long QTc increased with age 50-60 years and 60-70 years and 70-83 years (7.89%, 9.06%, 14.06%), respectively. There was no statistically significant difference between the genders (p > 0.05). Conclusion: The peak incidences of long and short QTc existed in two separate age groups in the healthy sample. The peak incidence of short QTc was in the age group of 18-40 years, and the peak incidence of long QTc was in the age group beyond the 50 years. For these two age groups, it was recommended to pay close attention to the changes in their QTc in order to prevent cardiovascular events.

Variables electrocardiográficas asociadas a la aparición de eventos cardiovasculares adversos en el infarto agudo de miocardio sin elevación del segmento ST / Electrocardiographic variables associated to the occurrence of adverse cardiovascular events in non-ST elevation acute myocardial infarction

Introducción: La frecuencia de infarto agudo de miocardio sin elevación del segmento ST se está incrementando y, con ella, los resultados adversos en pacientes con enfermedad coronaria isquémica aguda. Objetivo: Identificar las variables electrocardiográficas asociadas a la aparición de eventos cardiovasculares adversos en el infarto agudo de miocardio sin elevación del segmento ST. Método: Se realizó un estudio transversal, de tipo correlacional, con 68 pacientes con infarto agudo de miocardio sin elevación del segmento ST atendidos en el Hospital Arnaldo Milián Castro, en la provincia de Villa Clara. Se estudiaron los hallazgos electrocardiográficos y eventos cardiacos adversos durante el ingreso. Se hicieron análisis bivariados para establecer la relación de ambas variables, utilizando el estadígrafo chi cuadrado y el riesgo relativo. Resultados: Los hallazgos electrocardiográficos más frecuentes fueron la inversión de la onda T (#8805; 2mm), depresión del segmento ST y el QT corregido largo mediante la fórmula de Bazzet. El 26,5 por ciento presentaron eventos cardiovasculares adversos. La depresión del segmento ST, el QT largo corregido y la elevación del segmento ST en aVR se asociaron significativamente con eventos adversos intrahospitalarios (p lt; 0,05). Conclusiones: La asociación de la depresión del segmento ST, la elevación del segmento ST en aVR y el QT largo corregido con la ocurrencia de eventos cardiovasculares adversos intrahospitalarios, sugiere que estos hallazgos se pueden tener en cuenta como posibles indicadores de evolución desfavorable en pacientes con infarto agudo de miocardio sin elevación del segmento ST(AU)

Introduction: The frequency of non-ST elevation acute myocardial infarction is on the increase, and so is the number of adverse results in patients with acute ischemic coronary disease. Objective: Identify the electrocardiographic variables associated to the occurrence of adverse cardiovascular events in non-ST elevation acute myocardial infarction. Method: A cross-sectional correlational study was conducted of 68 patients with non-ST elevation acute myocardial infarction cared for at Arnaldo Milián Castro Hospital in the province of Villa Clara. Attention was paid to electrocardiographic findings and adverse cardiac events occurring during the hospital stay. Bivariate analyses were performed to establish the relationship between the two variables, using the chi square statigram and relative risk estimation. Results: The most common electrocardiographic findings were T-wave inversion (#8805; 2 mm), ST depression and long corrected QT by Bazzet's formula. Of the total study subjects 26.5 percent had adverse cardiovascular events. ST depression, long corrected QT and ST elevation in aVR were significantly associated to in-hospital adverse events (p < 0.05). Conclusions: Association of ST depression, ST elevation in aVR and long corrected QT with the occurrence of adverse in-hospital cardiovascular events suggests that these findings may be taken into account as possible indicators of an unfavorable evolution in patients with non-ST elevation acute myocardial infarction(AU)

Effect of CO2 Insufflation on Corrected QT Interval Prolongation during Laparoscopic Surgeries: A Prospective Observational Study

Introduction: Laparoscopic surgeries in various surgical specialties are most routinely performed with general anesthesia. Thephysiological effects of intra-abdominal CO2 insufflation combined with the variations in patient positioning can have a majorimpact on cardiorespiratory function. Prolongation of corrected QT interval (QTc) has been known to predispose torsades depointes, a potentially fatal ventricular arrhythmia may occur during CO2 insufflation. Our aim is to evaluate the effect of insufflationof CO2 on QT interval and QTc during prolonged laparoscopic surgeries.Methodology: Fifty patients of American Society of Anesthesiologists physical status 1 and 2, of either sex, between the agesof 25 and 65 years posted for laparoscopic surgeries included in the study. After general anesthesia, we measured mean arterialpressure, heart rate, SpO2 and ETCO2 before anesthesia induction, before CO2 insufflation, 30, 60, 120, and 150 min after CO2insufflation, 5 min after CO2 deflation, and at the end of surgery. We observed statistically significant increase of QTc intervalaround 120 min after CO2 insufflation.Conclusion: The cause of this QTc interval prolongation is multifactorial and clinical significance of producing life-threateningcardiac arrhythmias has to be determined.

Prevalence of prolonged corrected QT interval and its impact on outcomes in patients admitted in medical intensive care unit

Background: The long QT syndrome (LQTS) is a disorder of myocardial repolarization characterized by a prolonged QT interval on the electrocardiogram (ECG). Hence the present study was aimed to determine prevalence of QT prolongation of the ECG and to assess its impact on outcomes in patients admitted in medical ICU of Noor Hospital of IIMSR Medical College, Badnapur, Jalna, Maharashtra, India.Methods: This prospective observational study was carried out during the period of October 2016 to March 2018, for assessment of prevalence of prolonged QTc at admission and its impact on outcomes in medical ICU. QTc calculated by bazett’s formula of >440 ms for males and >460 ms for females was considered as prolonged. Details of illness, clinical observations and laboratory parameters were also monitored.Results: The total 150 patients were studied and there was a high prevalence (32%) of prolonged QTc at admission to the ICU which reduced to 20.5% on day 3. Patients with prolonged QTc were found to be at high risk for adverse outcomes and their ICU and hospital stay was more.Conclusions: The study concluded that prolonged QTc is common in authors’ medical ICU at admission (32%). Patients with QTc prolongation were at higher risk for adverse outcomes and their ICU and hospital stay was more.

Application of Multigene Panel Sequencing in Patients with Prolonged Rate-corrected QT Interval and No Pathogenic Variants Detected in KCNQ1, KCNH2, and SCN5A

Long QT syndrome (LQTS) is an inherited cardiac disease characterized by a prolonged heart rate-corrected QT (QTc) interval. We investigated the genetic causes in patients with prolonged QTc intervals who were negative for pathogenic variants in three major LQTS-related genes (KCNQ1, KCNH2, and SCN5A). Molecular genetic testing was performed using a panel including 13 LQTS-related genes and 67 additional genes implicated in other cardiac diseases. Overall, putative genetic causes of prolonged QTc interval were identified in three of the 30 patients (10%). Among the LQTS-related genes, we detected a previously reported pathogenic variant, CACNA1C c.1552C>T, responsible for cardiac-only Timothy syndrome. Among the genes related to other cardiac diseases, a likely pathogenic variant, RYR2 c.11995A>G, was identified in a patient with catecholaminergic polymorphic ventricular tachycardia. Another patient who developed dilated cardiomyopathy with prolonged QTc interval was found to carry a likely pathogenic variant, TAZ c.718G>A, associated with infantile dilated cardiomyopathy. Comprehensive screening of genetic variants using multigene panel sequencing enables detection of genetic variants with a possible involvement in QTc interval prolongation, thus uncovering unknown molecular mechanisms underlying LQTS.

Relationship between QT interval(QT)and metabolic syndrome / 实用医学杂志

Objective To investigate correlation between QT interval(QT),corrected QT interval(QTc) and metabolic syndrome(MS). Methods Residents who participated in our survey concerning atherosclerosis and related diseases conducted in Shenyang were included. They accomplished questionnaire,physical examination, laboratory tests and electrocardiography test. We divided them into MS group and non-metabolic syndrome (NMS)group according to International Diabetes Federation(IDF)diagnostic criteria for MS. QT interval was measured from the standard 12-lead electrocardiogram. QTc was calculated by using Bazett and Fridericia equations. We analyze correlation of QT ,QTc and MS. Results A total of 739 residents who were 35~64 years old were included. Individuals with MS had longer QTcB and QTcF than NMS group[(415.8 ± 31.9)ms vs.(410.1 ± 32.1)ms, (407.2± 29.1)ms vs.(402.6 ± 28.8)ms,P<0.05]. The more the number of abnormal MS parameters they had, the longer the QT,QTcB and QTcF they had. Regression analysis showed that QT was associated with serum potassium,smoking,blood glucose,and LDL,and QTcB and QTcF were associated with hypertension,waist circumference and blood potassium. Conclusions MS is associated with corrected QTc. Careful ECG monitoring among persons with MS for early detection of a long corrected QT interval may prevent severe and often fatal arrhythmias or sudden death.

Association between physical performance and electrocardiographic heart rate corrected-QT interval in elderly subjects / 体力科学

It is well known that decreased physical performance induces the decreased activity of daily living and increment of mortality rate in elderly subjects. On the other hand, a prolonged heart rate corrected-QT (QTc) interval is associated with an increased risk of cardiac sudden death and cardiac autonomic dysfunction. We investigated the associations between physical performance and QTc interval in elderly subjects. The subjects included 605 elderly persons (274 men and 331 women, age; 71.2±4.7 years) without a history of cardiovascular disease and taking cardioactive drugs. Resting 12-leads electrocardiography was measured after more than 5 minutes of rest. The QTc interval was calculated according to Bazett’s formula. The physical fitness test was performed to determine the physical performance (muscle strength, balance and walking abilities). The subjects were divided into four categories, which were defined as equally quantile distributions of QTc interval. The physical performance levels were significantly lower in the longest QTc interval group compared to the shortest QTc interval group in both men and women (p<0.05, respectively). Moreover, after adjusting for the age, the physical performance levels were significantly lower in the longest QTc interval group compared to the shortest QTc interval group, especially, this relationship was observed in late-stage elderly group (p<0.05, respectively). These results suggest that decreased physical performance levels were also associated with prolonged QTc interval in elderly subjects.

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/radicalRR) 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.

Heart rate variability predicts the extent of corrected QT interval prolongation after tracheal intubation

BACKGROUND: Corrected QT (QTc) interval can be modulated by sympathetic and parasympathetic balance. Tracheal intubation causes significant prolongation of the QTc interval due to sympathetic stimulation. This study was designed to elucidate the relationship between baseline autonomic nervous system activity and QTc prolongation after endotracheal intubation using heart rate variability (HRV). METHODS: Sixty-six healthy patients were included and the baseline HRV data were recorded for 5 min before anesthesia. Power spectrum densities were calculated for low frequencies (LF, 0.04-0.15 Hz) and high frequencies (HF, 0.15-0.4 Hz), defined as either LF's or HF's relative part of the total power. Anesthesia was induced with sevoflurane and vecuronium was given. The QTc interval, heart rate (HR) and mean arterial pressure (MAP) were measured before induction (baseline), before laryngoscopy (pre-intubation) and immediately after the intubation (post-intubation). RESULTS: The QTc interval change at post-intubation from baseline (DeltaQTc) showed a significant negative correlation with the HF (r = 0.34, P = 0.006) and positive correlation with LF/HF ratio (r = 0.37, P = 0.005). Patients were retrospectively divided into low-HF/LF (2.5, n = 22). The DeltaQTc was statistically higher in the high-LF/HF group compared to that in the low-LF/HF group (P = 0.048). The HR and MAP at baseline, pre-intubation and post-intubation were not different between two groups. CONCLUSIONS: The QTc interval prolongation after endotracheal intubation is influenced by baseline autonomic conditions and can be exaggerated in patients with activated sympathetic activity or depressed parasympathetic activity.

Correlation of anthropometric parameters with QTc interval in malnourished children.

Various studies have reported the effect of severe malnutrition on electrolyte levels and electrocardiographic parameters. However, only a few have reported these findings in mild and moderate grades of malnutrition in children. Therefore, the objective of this study was to assess the effect of malnutrition (mainly mild and moderate grades) on corrected QT interval (QTc) and QT dispersion (QTcd) and electrolyte changes. A total of 20 malnourished children in the age group of 2-11 yrs were enrolled in the study group and 20 age and sex matched healthy children were taken as controls. Anthropometry, serum levels of albumin & electrolytes were determined. QTc and QTcd (difference between maximum & minimum corrected QT interval) were measured with the help of RMS Polyrite D. Our results have shown that body weight, height, body mass index (BMI), serum levels of albumin, potassium & calcium were lower (P<0.01) in malnourished children. QTc (P<0.01) & QTcd (P<0.01) were significantly greater in malnourished children than controls. We concluded that increase in QTc and QTcd intervals is associated with electrolyte disturbances in malnourished children. Electrolyte disturbance correction and appropriate nutrition therapy followed by further cardiac evaluation must be taken into account in the management of these patients.

Intervalo QT corrigido e fatores de risco tradicionais para doença aterosclerótica em pacientes com diabetes tipo 1 / QTc Interval and traditional risk factors to atherosclerotic disease in patients with type 1 diabetes

Visando avaliar o intervalo QTc e sua relação com variáveis clínicas, laboratoriais e com suscetibilidade da LDL à oxidação in vitro em pacientes com DM1, estudamos 40 diabéticos e 33 não diabéticos com idades de 24,83 ± 10,21 e 23,51 ± 7,28 anos, respectivamente, pareados por sexo, idade e índice de massa corporal (IMC). Avaliamos controle metabólico, apolipoproteínas A e B, coeficiente de oxidação da LDL por espectrofotometria e eletrocardiograma (ECG). O intervalo QTc foi calculado pela fórmula de Bazett. Não houve diferença no QTc entre os grupos dos DM1 e dos não diabéticos (394,43 ± 19,98 ms vs. 401,31 ± 17,83 ms; p = 0,2065). Cinco diabéticos apresentavam QTc aumentado (396,76 ± 14,63 ms vs. 429,75 ± 1,89 ms; p < 0,001) e menores níveis de apolipoproteína A que os demais diabéticos (74,60 ± 25,42 mg/dL vs. 113,64 ± 29,79 mg/dL; p = 0,011). Na amostra total, houve correlação entre QTc e IMC (rho = -0,288; p = 0,045), glicemia pós-prandial (rho = 0,357; p = 0,016) e coeficiente de oxidação 3 h (Cox3h) (r = -0,293; p = 0,039). Nos diabéticos, encontramos correlação entre QTc e triglicerídeos (rho = -0,420; p = 0,023) e Cox3h (r = -0,427; p = 0,021). Embora não tenhamos encontrado diferença entre o QTc dos diabéticos e não diabéticos estudados, houve correlação com marcadores de risco para a doença aterosclerótica. Entretanto, ainda são necessários mais estudos para estabelecer o real valor preditivo do QTc para esta doença nos pacientes com DM1.

To evaluate the QTc interval and its relation with clinical, laboratorial variables and LDL susceptibility to in vitro oxidation in patients with type 1 DM, we studied 40 diabetics and 33 non diabetics with 24.83 ± 10.21 and 23.51 ± 7.28 years old, respectively matched by sex, age and body mass index (BMI). We evaluated metabolic control, A and B apolipoproteins, LDL oxidation coefficient for spectrophotometry and electrocardiogram (ECG). Interval QTc was calculated by the Bazett’s formula. There was no difference in QTc between diabetic and non diabetic groups (394.43 ± 19.98 ms versus 401.31 ± 17.83 ms; p = 0.2065). Five diabetics showed increased QTc (396.76 ± 14.63 ms versus 429.75 ± 1.89 ms; p < 0.001) and lesser A apolipoprotein levels than rest of diabetic group (74.60 ± 25.42 mg/dL versus 113.64 ± 29.79 mg/dL; p = 0,011). In pooled sample, there was correlation between QTc and BMI (rho = -0.288; p = 0.045), pot-prandial glycemia (rho = 0.357; p = 0.016) and 3 h oxidation coefficient (OxC3h) (r = -0.293; p = 0.039). In diabetics, there was correlation between QTc and triglycerides (rho = -0.420; p = 0.023) and OxC3h (r = -0.427; p = 0.021). Although there was no difference between QTc of diabetics and the non diabetics subjects studied, there was correlation with risk factors for the atherosclerotic disease. Further studies are necessary to establish the real predictive value of QTc for this type of disease in the patients with type 1 DM.

Wavelet transform for QT interval measurement in ordinary ECG / 医疗卫生装备

This paper mainly introduces a new method for detection of QT interval in ordinary ECG. As the interval between QRS waves and T wave in ECG, QT interval represents the depolarization of ventricle. QT interval and its aberrance can be used to forecast malignant abnormalities of heart rate. Wavelet transform is a time scale analysis method of the signal. It has a high frequency resolution and a low time resolution for the low-frequency part of the signal, and has a high time resolution and a low frequency resolution for the high-frequency part. On the basis of the characteristics of the starting point of QT interval, the second derivative of Gaussian function is adopted as the wavelet basis and applied to multi-scale transform of ECG signal. The waveforms with QRS waves as starting point and T wave as the end point are selected as the subjects. Then the measurement result is transformed into corrected QT interval, that is, QTC. QTC can be applied to forecasting the diseases.