Repolarization characteristics and incidence of torsades de Pointes in patients with acquired complete atrioventricular block.ABSTRACT
Objective: Torsades de pointes Torsades de pointes or torsades is a French term that literally means "twisting of the points". It was first described by Dessertenne in 1966 and refers to a specific variety of ventricular tachycardia that exhibits distinct characteristics on the (TdP) during bradyarrhythmias have been reported to be associated with gender, degree of QT prolongation and duration of bradyarrhythmia. We sought to investigate the repolarization repolarization /re·po·lar·iza·tion/ (re-po?ler-i-za´shun) the reestablishment of polarity, especially the return of cell membrane potential to resting potential after depolarization. characteristics on 12-lead electrocardiogram electrocardiogram /elec·tro·car·dio·gram/ (-kahr´de-o-gram?) a graphic tracing of the variations in electrical potential caused by the excitation of the heart muscle and detected at the body surface. (ECG ECG electrocardiogram.
Also called an electrocardiogram, it records the electrical activity of the heart. ) and the incidence of TdP in patients with acquired complete atrioventricular block (CAVB).
Methods: Fifty consecutive patients with acquired CAVB were included in the study. Patients with coronary artery disease coronary artery disease, condition that results when the coronary arteries are narrowed or occluded, most commonly by atherosclerotic deposits of fibrous and fatty tissue. , systolic Systolic
The phase of blood circulation in which the heart's pumping chambers (ventricles) are actively pumping blood. The ventricles are squeezing (contracting) forcefully, and the pressure against the walls of the arteries is at its highest. dysfunction and previous cardiac surgery were excluded. Patients were monitored during hospitalization for ventricular arrhythmias (VA). Serum potassium, magnesium, calcium levels and thyroid-stimulating hormone were measured. Heart rate, (IRS An abbreviation for the Internal Revenue Service, a federal agency charged with the responsibility of administering and enforcing internal revenue laws. duration, QT/QTc, JT/JTc and Tpeak-Tend intervals were measured. Pathologic U waves, T-U complex, and QT morphologies were remarked.
Results: Patients presented with presyncope (n=39, 78%), syncope syncope
Effect of temporary impairment of blood circulation to a part of the body. It is often used as a synonym for fainting, which is loss of consciousness due to inadequate blood flow to the brain. (n=12, 24%), and palpitations (n=8,16%). All patients were in sinus rhythm. Duration of CAVB was 8.5 days (median). Patients were divided into two groups based on JT interval. Group 1 (JT [greater than or equal to] 500 ms, n=13) tended to have more female patients and more VAs in comparison to Group 2 (JT<500 ms, n=37). Group 1 patients had more pathologic U waves and T-U complexes, longer Tpeak-Tend intervals , and more long QT2 syndrome (LQT LQT Long QT 2)-like QT morphology in comparison to Group 2 patients. Group 2 patients had more often syncope. One patient in Group 2 developed ventricular fibrillation in the presence of hypokalemia Hypokalemia Definition
Hypokalemia is a condition of below normal levels of potassium in the blood serum. Potassium, a necessary electrolyte, facilitates nerve impulse conduction and the contraction of skeletal and smooth muscles, including the heart. and hypomagnesemia hypomagnesemia /hy·po·mag·ne·se·mia/ (-mag?nes-em´e-ah) abnormally low magnesium content of the blood.
An abnormally low level of magnesium in the blood. .
Conclusion: Torsades de Pointes during CAVB was rare among our patient population. The predictors of VA during CAVB were presence of prolonged QTc/JTc intervals, pathologic U wave and T-U complex, prolonged Tpeak-Tend interval, and LQT2-like QT morphology.
Keywords: Torsade de Pointes tor·sade de pointes
Paroxysms of ventricular tachycardia in which the electrocardiogram shows a steady undulation in the QRS axis in runs of 5 to 20 beats and with progressive changes in direction. , heart block, repolarization, QT interval, JT interval
Bradyarrhythmias, including complete atrioventricular block (CAVB), may predispose pre·dis·pose
To make susceptible, as to a disease. to acquired long-QT syndrome (L(ITS) and torsade de pointes (TdP) (1). Torsades de Pointes (TdP) was first described in a patient with acquired CAVB (2). Between 5% to 30% of patients with CAVB have been reported to develop TdP (3). Kurita et al. (4) have reported that patients with bradycardia bradycardia: see arrhythmia. induced TdP have abnormally long QT intervals at slow heart rates, compared with patients with bradycardia but no tachyarrhythmia tachyarrhythmia /tachy·ar·rhyth·mia/ (tak?e-ah-rith´me-ah) any disturbance of the heart rhythm in which the heart rate is abnormally increased.
n. . Moroe et al (5) have reported that in patients with CAVB associated with prolonged QTc interval frequent ventricular premature beats might induce TdP. Also Strasberg et al. (6) have reported that QT interval above 600 ms and premature ventricular beats on electrocardiogram (ECG) seem to indicate an increased risk for the development of polymorphic ventricular tachycardia in a patient with atrioventricular block (AVB AVB Allgemeine Versicherungsbedingungen
AVB Armin Van Buuren (musician)
AVB Atrioventricular Block
AVB Association Vaincre le Bègaiement
AVB Acappella Vocal Band (men's Christian a cappella group) ) (6). In addition, increased propensity of women to develop TdP during CAVB has been reported (7).
In vivo studies showed that the duration of AVB is an important determinant of the susceptibility to acquired TdP, because the TdPs are rarely inducible at 0 weeks of AVB (acute AVB) or at sinus rhythm but are readily inducible at [greater than or equal to] 5 weeks (chronic AVB) in most animals (8). The increased susceptibility to arrhythmias in chronic AVB has been related to an inhomogeneous Adj. 1. inhomogeneous - not homogeneous
heterogeneous, heterogenous - consisting of elements that are not of the same kind or nature; "the population of the United States is vast and heterogeneous" prolongation of the monophasic ventricular action potential At rest, the ventricular myocyte membrane potential is about -90 mV, which is close to the potassium reversal potential. When an action potential is generated, the membrane potential rises above this level in four distinct phases. (more in the left ventricle than the right ventricle), leading to enhanced regional dispersion of repolarization (8). We sought to investigate the repolarization characteristics on 12-lead ECG and the incidence of TdP in patients with acquired CAVB.
Seventy two consecutive patients presenting with acquired CAVB were retrospectively included in the study, between January 2001 and December 2006. Patients with acute coronary syndrome acute coronary syndrome
A sudden, severe coronary event that mimics a heart attack, such as unstable angina.
acute coronary syndrome , history of coronary artery disease, left ventricular systolic dysfunction (left ventricular ejection fraction <50%), congenital CAVB, and previous cardiac surgery were excluded (n=22). The remaining 50 patients formed the study population.
Every patient had 12-lead ECGs before the permanent/temporary pacemaker implantation. All patients had serial serum creatine creatine /cre·a·tine/ (kre´ah-tin) an amino acid occurring in vertebrate tissues, particularly in muscle; phosphorylated creatine is an important storage form of high-energy phosphate. kinase-MB and cardiac troponin I measurements. Serum potassium, magnesium, calcium levels and thyroid-stimulating hormone were measured in all patients.
The 12-lead ECGs were recorded at standard gain (10 mV/mm) and speed (25 mm/s). Heart rate, (IRS duration, QT and corrected QT (QTc) intervals, JT and corrected JT (JTc) intervals, Tpeak-Tend intervals were measured. Cardiac rhythm, presence or absence of pathologic U wave or T-U complex, QT morphologies, inverted inverted
reverse in position, direction or order.
inverted L block
a pattern of local filtration anesthesia commonly used in laparotomy in the ox. T waves (>3mV), intraventricular conduction disturbances, frequent ventricular premature contractions (PVC PVC: see polyvinyl chloride.
in full polyvinyl chloride
Synthetic resin, an organic polymer made by treating vinyl chloride monomers with a peroxide. ) ([greater than or equal to] 10/hour), couplets and ventricular tachycardias (VT) were remarked.
The QT interval was measured from the onset of the (IRS interval to the end of the T wave in all the leads where the end of the T wave could be clearly defined. The JT interval was derived by subtracting the (IRS duration from the QT interval. The QT and JT intervals were corrected for the heart rate using the Bazett formula (QTc and JTc) (9). Pathologic U wave was defined as U wave with an amplitude of greater than 25% of the of T wave. T-U complex was defined as two contiguous repolarization waves, the first being T wave and the second being U wave (10, 11). Tpeak-Tend was the interval from the summit of the T wave to the end of the QT interval. T wave morphology was defined as in the congenital Long QT syndrome The long QT syndrome (LQTS) is a heart condition associated with prolongation of repolarisation (recovery) following depolarisation (excitation) of the cardiac ventricles. It is associated with syncope (fainting) and sudden death due to ventricular arrhythmias. (LQTS LQTS Long QT interval syndrome, see there ): 1) "LQT1-like morphology" denoted a long QT interval (QTc interval [greater than or equal to] 450 ms) with broad T waves; 2) "LQT2-like morphology" denoted a long QT interval with double (notched) T waves; and 3) "LQT3-like morphology" denoted a long QT interval with small T waves separated from the (IRS interval by a long isoelectric isoelectric /iso·elec·tric/ (i?so-e-lek´trik) showing no variation in electric potential.
showing no variation in electric potential. ST-segment (12, 13). Torsades de pointes was defined as a ventricular tachycardia (rate>than 150 beats/min and lasting [greater than or equal to] 5 beats) that originated from the terminal part of the QT interval and had a polymorphic configuration (13). Intraventricular conduction disturbances were defined as previously described (14). Measurements were made with caliper caliper
Instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts. Spring calipers have an adjusting screw and nut; firm-joint calipers use friction at the joint to hold the legs unmoving. in leads with longest QT interval.
Previous studies advocated the use of JT interval instead of the QT interval as a result of secondary prolongation of the QT interval due to prolonged excitation time in ventricular conduction defects. Since significant number of patients in our study had intraventricular conduction delay, we used JT and JTc intervals rather than QT and QTc intervals for the evaluation of the repolarization.
All patients underwent transthoracic echocardiography for the measurements of right and left ventricular ejection fractions, right and left ventricular wall thicknesses, and end-systolic/ diastolic Diastolic
The phase of blood circulation in which the heart's pumping chambers (ventricles) are being filled with blood. During this phase, the ventricles are at their most relaxed, and the pressure against the walls of the arteries is at its lowest. chamber diameters.
Values were expressed as mean [+ or -] SD. Characteristics of groups were compared using the unpaired Students t-test and p<0.05 was considered as statistically significant. Categorical variables were compared using Chi-square analysis.
Study population consisted of 50 patients (30 women/20 men; mean age 75 [+ or -] 10 years, range 46 to 92). Patients presented with presyncope (n=39, 78%), syncope (n=12, 24%), and palpitations (n=8, 16%). All patients were in sinus rhythm. Intraventricular conduction delay was observed in 31 (62%) patients. Duration of CAVB was 8.5 days (median).
Study population was divided into two groups based on JT interval. Characteristics of Group 1 (JT [greater than or equal to] 500 ms, n=13) and Group 2 (JT < 500 ms, n=37) patients are summarized in Table 1.
Group 1 patients tended to have more female patients and more ventricular arrhythmias in comparison to Group 2 patients. Group 1 patients had more pathologic U waves and T-U complexes (p=0.0001), longer Tpeak-Tend intervals (p<0.0001), and more LQT2-like QT morphology (p=0.005) in comparison to Group 2 patients. Group 2 patients had more episodes of syncope (p>0.05). There were two patients taking "possible" (IT prolonging agents in Group 2. One patient in Group 2 developed ventricular fibrillation in the presence of hypokalemia and hypomagnesemia. This patient presented with presyncope and had QTc of 480 ms and JTc of 360 ms.
Complete AVB may lead to downregulation of potassium channels, QT interval prolongation, and TdP (15, 16). Episodes of TdP may result in syncope, cardiac arrest, and even death due to degeneration into ventricular fibrillation. Also, repolarization changes secondary to CAVB may indicate underlying potassium channelopathies (mutations and polymorphisms) (17). Therefore, identification of patients at risk of developing TdP and cardiac events is crucial. For this purpose new risk factors such as Tpeak-Tend interval and LQT2-like notched T waves have been described recently. In our study, patients with prolonged QTc and JTc intervals had more pathologic U wave and T-U complex and LQT2-like notched T waves.
The rarity of TO in our study population can be partly explained by genetic composition of Turkish population. Chevalier et al. (17) recently described HERG HERG Human Ether-a-Go-go Related Gene
HERG Herring Gull (bird species)
HERG Henipavirus Ecology Research Group mutations in 17% of patients presenting with CAVB and prolonged QT interval (>600 ms) in a French population. None of the patients with CAVB and shorter QT interval (<600 ms) had HERG mutations. These mutations may not be common in Turkish population. As a result, further studies are needed for identification of genetic risk factors in this group of patients.
Roden et al. (18) have suggested that the extent of QT lengthening in response to specific environmental triggers depends on the "ventricular repolarization reserve". As a consequence, under baseline conditions, mutations in genes controlling normal repolarization may remain subclinical subclinical /sub·clin·i·cal/ (sub-klin´i-k'l) without clinical manifestations.
Not manifesting characteristic clinical symptoms. Used of a disease or condition. and may only be the source of clinical and electrocardiographic electrocardiographic
emanating from or pertaining to electrocardiography.
maintenance of a more or less continuous surveillance of a patient's cardiac status by means of electrocardiography. manifestations of the LQTS upon exposure to further stressors, such as drugs or bradycardia. Low incidence of QT prolonging drug use, normal serum potassium levels, and genetic background may explain the rarity of TO in our study population.
Genotype analysis was not performed for LQTS genes in our patients.
Torsades de pointes during CAVB was rare among our patient population. The predictors of ventricular arrhythmia during CAVB were presence of prolonged QTc/JTc intervals, pathologic U wave and T-U complex, prolonged Tpeak-Tend interval, and LQT2-like QT morphology.
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Yasemin Turan Bozkaya, Zuhal Eroglu, Meral Kayikcioglu, Serdar Payzin, Levent H. Can, Hakan Kultursay, Can Hasdemir
From Department of Cardiology, School of Medicine, Ege University, Izmir, Turkey
Address for Correspondence: Yasemin Turan Bozkaya, MD, Department of Cardiology, School of Medicine, Ege University, Izmir, Turkey Phone: +90 232 390 40 01 Fax: +90 232 390 32 87 E-mail: email@example.com
Table 1. Clinical and electrocardiographic characteristics of patients Variables Group 1 Group 2 p Age, years 76 [+ or -] 9 75 [+ or -] 10 NS Gender, Female/Male 39338 21/37 NS Presence of syncope, n (%) 1(7) 11(30) NS Duration of AV block, days * 10 7 NS Presence of VA, n (%) 2(15) 2(5) NS Presence of LVH, n (%) 5(38) 10(27) NS RR interval, ms 1660 [+ or -] 300 1610 [+ or -] 260 NS QRS duration, ms 122 [+ or -] 26 136 [+ or -] 31 NS QT, ms 677 [+ or -] 41 545 [+ or -] 59 <0.0001 QTc, ms 529 [+ or -] 45 431 [+ or -] 41 <0.0001 JT, ms 555 [+ or -] 37 409 [+ or -] 52 <0.0001 JTc, ms 434 [+ or -] 42 324 [+ or -] 36 <0.0001 Tpeak-Tend, ms 268 [+ or -] 75 146 [+ or -] 43 <0.0001 U wave/T-U complex, n (%) 8 (62) 3(8) <0.0001 Serum potassium, mEq/l 4.2 [+ or -] 0.6 4.4 [+ or -] 0.7 NS QT prolonging agent, n (%) 0 2 (5) NS LQT1-like QT morphology, n (%) 3(23) 8(22) NS LQT2-like QT morphology, n (%) 7(54) 3(8) 0.005 LQT3-like QT morphology, n (%) 1(8) 0 NS Data are given as mean [+ or -] SD, number of patients, percentages, and * median. p<0.05 considered to be significant. AV- atrioventricular, LQT- long QT syndrome, LVH- left ventricular hypertrophy, NS- non significant, VA- ventricular arrhythmia (premature ventricular contraction, couplet, ventricular tachycardia and ventricular fibrillation)