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Results for “QTc interval prolongation”

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At least 19 recordsLinked to original sources

PubMed1977

Evolutionary changes in the electrocardiogram of severe progressive hypothermia.

A patient is reported who developed progressive hypothermia during therapy for adult respiratory distress syndrome. Electrocardiographic changes (sinus bradycardia, prolonged PR interval, prolonged QTc interval, "Osborn waves") were documented and correlated with body temperature. The significance of these changes is discussed and the relationship between the degree of hypothermia and the presence of "Osborn waves" is noted.

Adult↗

PubMedDate not supplied

Certain observations in electrocardiogram and enzyme variation in dogs, following scorpion venom injection.

The effect of scorpion venom of Buthus Tamulus species on blood pressure, ECG, enzyme and electrolytes were studied in dogs. Venom was given in doses of 2 and 4 mg/kg body weight. Hypotension and tachycardia were observed with low dose and bradycardia was significant with high dose. ST segment depression, T wave changes, shortening of PR interval were the important ECG changes apart from ventricular extrasystoles. With high dose, QRS amplitude was reduced and duration prolonged. QTC interval was also significantly prolonged. Significant increase in SGOT, SGPT and LDH levels were observed but no change in serum electolytes was seen.

Alanine Transaminase↗

PubMed2026

Development of Electrocardiography Standards for Evaluating Myocardial Infarction and Ischemia-Reperfusion Injury in Mice.

BACKGROUND: Acute and chronic heart failure secondary to myocardial infarction (MI) and cardiac ischemia-reperfusion injury (IRI) are leading causes of death in ischemic heart disease. A mouse model is indispensable for investigating MI and IRI, and the development of reliable mouse MI and IRI models is essential for advancing research in this field. The clear early diagnostic criteria for confirming successful induction of MI and IRI in mice remain lacking. METHODS: Adult C57BL/6J background mice underwent left anterior descending coronary artery ligation to induce acute MI, or ligation followed by reperfusion to induce IRI. The success of the MI and IRI model establishment was confirmed by 2,3,5-triphenyltetrazolium chloride staining and echocardiography. Electrocardiography was used to monitor the electric activity in the mice. CONCLUSIONS: Electrocardiography demonstrated that ST-segment elevation in ECG lead II and corrected QTc interval prolongation at 30 minutes following left anterior descending ligation as 2 key early indicators of successful MI. Echocardiography analysis revealed that the magnitude of ST-segment elevation strongly correlated with the left anterior descending ligation site, where a more proximal ligation produced a greater ST-segment elevation amplitude and more severe ischemia. In IRI models, ST-segment elevation typically resolved and returned to baseline within 20 minutes of reperfusion. This study developed quantifiable early diagnostic criteria for successful MI and IRI induction based on characteristic ECG changes. These quantifiable ECG parameters provide early diagnostic standards that can significantly streamline and optimize modeling procedures.

Animals↗

PubMed1978

Cardiac complications of protein-sparing modified fasting.

Cardiovascular abnormalities developed in a patient during a protein-sparing modified fasting diet. Syncope was the complaint at the time of examination. Hypotension, persistent QTc interval prolongation, and a low QRS voltage were observed before the development of refractory ventricular tachycardia. At autopsy, antemortem thrombi were attached to the left ventricular endocardium and a fenestrated aortic valvule. Strick protein-sparing modified fasting is not without risk of sudden death even with close medical supervision.

Adult↗

PubMed1977

The effects of oral propranolol, digoxin and combination therapy on the resting and exercise electrocardiogram.

The effects of propranolol, digoxin and combination therapy (/D) on the resting and exercise ECG were studied in ten normal subjects and 20 patients with coronary artery disease (CAD) given a sequence of oral placebo, propranolol, P/D, digoxin and placebo, for two week periods. Digoxin produced a significant decrease in T-wave amplitude and often resulted in ST segment depression in the resting ECG. Propranolol, digoxin, and P/D tended to decrease the QTc interval and prolong the PR interval. However, CAD patients were more sensitive to PR prolongation than normals while receiving propranolol or digoxin alone. Propranolol therapy did not significantly affect the ST segment of the exercise ECG in the normal subjects or the CAD patients without an ischemic control exercise ECG. By contrast, 50 per cent of the normal subjects developed "false-positive" ischemic ST segment responses to exercise while receiving digoxin of P/D and three of eight CAD patients without ischemic control exercise ST segments had a similar response to digoxin or P/D. In 12 CAD patients with ischemic control exercise ST segments, propranolol did not affect the amount of ST segment depression at the onset of angina or the maximum amount of ST segment depression. Digoxin or P/D both uniformly increased the maximum amount of ST segment depression which was greater with digoxin than P/D. However, the maximum heart rate on P/D was significantly reduced as compared to that on digoxin. It is concluded that (1) CAD patients are more sensitive to propranolol or digoxin-induced AV block than normals, (2) propranolol does not change the magnitude of ischemic exercise ST segment depression, (3) digoxin increases ischemic exercise ST segment depression and results in a high incidence of false-positive exercise tests, and (4) the addition of propranolol to digoxin attenuates the effects of digoxin on the exercise ST segment.

Administration, Oral↗

PubMed1992

Dofetilide, a novel class III antiarrhythmic agent.

Dofetilide is a potent and selective class III antiarrhythmic agent that is under development for the treatment of re-entrant tachyarrhythmias (ventricular tachycardia/ventricular fibrillation, atrial fibrillation/atrial flutter, and paraoxysmal supraventricular tachycardia). In animal studies, dofetilide selectively inhibits the rapid component of the time-dependent outward potassium current (IKr) and therefore increases the effective refractory period and action potential duration without affecting the fast inward sodium current. Studies in dogs have shown that dofetilide (a) prolongs the effective refractory period in a dose-dependent manner, (b) elevates ventricular fibrillation threshold, (c) facilitates conversion of electrically induced ventricular fibrillation or fibrilloflutter to sinus rhythm, (d) does not influence conduction within the His-Purkinje system or within the myocardium, (e) does not impair cardiac contractility, and (f) reduces dispersion of ventricular repolarization. Dofetilide has been administered to healthy volunteers as well as to patients with ischemic heart disease or with supraventricular arrhythmias; the compound has generally been well tolerated. Side effects have occasionally been reported, but have generally been transient and mild and occur in placebo-treated subjects as well. No clinically significant changes in laboratory safety tests have been detected. The pharmacokinetic profile of dofetilide both in healthy volunteers and patients includes a linear dose-plasma concentration relationship and also a linear plasma concentration-QTc relationship. The terminal plasma elimination half-life is approximately 9-10 h and systemic bioavailability in the region of 100%. The elimination pattern is balanced, with 50% being excreted unchanged via the kidney, the remaining 50% being metabolized in the liver to inactive metabolites, with greater than 90% of circulating drug-related material being unchanged dofetilide. After intravenous administration of the compound, a slight hysteresis in the plasma drug level-QTc relationship has been detected. Pharmacodynamic data demonstrate dose- and concentration-dependent effects on myocardial repolarization as evidenced by prolongations of the QTc interval. This is reflected in significant prolongations in the effective and functional refractory periods and monophasic action potential duration throughout the myocardium. No effects on sinus node function, conduction parameters, or cardiac contractility have been detected in any of the clinical studies, supporting the contention that dofetilide is a highly selective class III antiarrhythmic agent.

Action Potentials↗

PubMed1992

Role of QT interval at onset of acute myocardial infarction in predicting early phase ventricular arrhythmia.

In this study, the QTc interval was determined in 51 patients of acute myocardial infarction and the incidence of ventricular arrhythmias in them was noted. It was found that the QTc interval was prolonged (more than 0.44 sec) in all the 33 patients who developed ventricular arrhythmias, while it was below 0.44 sec in all the 18 patients who did not develop ventricular arrhythmia.

Adult↗

PubMed1992

Bepridil. A review of its pharmacological properties and therapeutic use in stable angina pectoris.

Bepridil is a calcium antagonist with direct negative chronotropic, dromotropic, inotropic and vasodilatory actions which reduces myocardial oxygen consumption and increases coronary blood flow, leading to a significant anti-ischaemic and antianginal effect in the absence of reflex tachycardia. In contrast to other calcium channel blockers, bepridil produces only modest peripheral vasodilatation and displays weak antihypertensive activity. Its plasma elimination half-life of 1 to 2 days permits once daily administration. Results of short term clinical trials have shown bepridil to be of comparable efficacy to nifedipine, verapamil, diltiazem, propranolol and nadolol in decreasing the frequency of anginal attacks and consumption of nitroglycerin (glyceryl trinitrate) in patients with stable angina. Bepridil is more effective than nifedipine in improving exercise performance in patients with stable angina. Although bepridil proved superior to diltiazem in improving exercise performance in patients refractory to diltiazem, further studies are required to confirm the efficacy of bepridil in patients refractory to, or intolerant of, other antianginal agents. Bepridil in therapeutic doses is well tolerated, and appears to have a similar adverse effect profile to the established calcium antagonists. However, rate-dependent prolongation of the QTc interval and development of torsade de pointes have been associated with the use of bepridil. Therefore, bepridil is contraindicated in patients with hypokalaemia, those receiving other drugs that may prolong the QT interval, and those with congenital QT interval prolongation. Future clinical research will help to further define the position of bepridil as an antianginal treatment relative to the traditional calcium antagonists; in the interim, bepridil is indicated for the treatment of patients with angina refractory to or intolerant of other agents.

Angina Pectoris↗

PubMed1975

Effects of amiodarone on thyroid function in patients with ischaemic heart disease.

Thyroid function was evaluated clinically and biochemically in 12 patients with ischaemic heart disease receiving 200 mg oral amiodarone three times daily for periods up to 6 weeks. During drug administration, no patient developed clinical or laboratory evidence of hypothyroidism, but serum levels of T3 tended to fall and those of T4 increased but not to levels outside the normal range. Amiodarone produced a significant reduction in heart rate with prolongation of the QTc interval of the electrocardiogram without altering either the PR interval or the QRS duration. These effects of the drug were still present 4 weeks after cessation of treatment. In spite of the high iodine content, amiodarone does not, therefore, depress thyroid function to any important degree during chronic administration and its antianginal action does not appear to be caused by the production of generalized hypothyroidism.

Amiodarone↗

PubMed1977

An unusual cause of apparent epilepsy: ECG and EEG findings in a case of Jervell Lange-Neilson syndrome.

A case is presented of apparent epilepsy which proved to be due to recurrent ventricular tachyarrhythmias (torsade de pointe). The relationship between the cardiac arrhythmia and changes in the electroencephalograph is recorded and analysed. This is probably an example of the 'Jervell Lange-Neilson' syndrome of cardiac arrhythmias which may produce ictal episodes, prolongation of the QTc interval of the ECG, and sensori-neural deafness. The features of the syndrome, its pathology and treatment, and its relevance to the mangement of epilepsy are discussed.

Adolescent↗

PubMed1979

Prolonged QT interval and cardiac arrhythmias in two neonates: sudden infant death syndrome in one case.

Two neonates with arrhythmias and the long QT syndrome are described. The arrhythmias were detected in utero and both infants were apparently well after birth. The first infant, although well, had a bradycardia for the first 9 days of life. A normal heart rate was documented at 10 days but a prolonged QT interval was not appreciated on the ECG. He was discharged from hospital but died suddenly and unexpectedly 3 days later. A post-mortem examination failed to find a cause for his death which therefore fell into the category of the sudden infant death syndrome (SIDS). A retrospective analysis of the perinatal electrocardiogram showed a probable junctional rhythm with 2:1 conduction to the ventricle; the QT interval was prolonged at 0.52 seconds (QTC = 0.63). The second infant had a QT interval of 0.52 seconds (QTC = 0.54) and frequent ventricular premature beats on a 24-hour electrocardiogram. She was treated with propranolol and remains well 2 years later. Sudden infant death has often been described in the siblings of children with the long QT syndrome and one other report described a case of SIDS which was said to have had a prolonged QT interval on the perinatal ECG. This report, however, provides unquestionable evidence, in one case, of an association between the long QT syndrome and SIDS.

Arrhythmias, Cardiac↗

PubMed1975

[Acute effect of lidoflazine on the electrocardiographic agitation discharge in atrial frequency stimulation (studies on patients with stress-induced coronary insufficiency)].

Electrocardiographic alterations and onset of angina pectoris during an acute treatment period with lidoflazine -3 to 4 mg/kg b.w. by oral application- was investigated in 20 patients with latent coronary insufficiency under increasing heart rate condition by atrial pacing. Significant changes in the repolarisation phase mainly due to prolongation of the QTc-interval already appeared 90 to 120 min after oral administration. The onset of test-induced agina pectoris and ischaemic ST-segmental depression in the ECG were not influenced by lidoflazine. Exceeding a rate of 140 min-1 produced a delay of atrioventricular conduction time under drug influence whereas significant changes of intraventricular conduction did not appear. Under frequent heart rates bundle branch block developed in a few individuals that might be drug-induced. In addition, there were some signs of digitalis-potentiation by lidoflazine.

Administration, Oral↗

PubMed1978

Cardiovascular effects of tricyclic and tetracyclic antidepressants.

Cardiovascular effects of therapeutic doses of tricyclic or tetracyclic antidepressants (TCA) were examined in 66 patients. After three weeks of therapy, heart rate and PR interval were increased (P less than .02, P less than .05), while prolongation of the QTc time and the QRS interval did not reach significant levels. We observed significant flattening of T waves (P less than .05), which was not associated with changes in the serum potassium level. These changes were reversible after treatment was discontinued. When therapy was maintained for 13 months, only the heart rate continued to be increased, whereas all other ECG values had returned to normal. The TCA therapy led to a significant prolongation of the preejection period (P less than .01) and slight shortening of the left ventricular ejection time, indicating a decrease in myocardial contractility. There was no difference of effects on the values studied between tricyclic and tetracyclic antidepressants.

Adult↗

PubMed1976

[Contribution to the effect of tri and tetracyclic antidepressive agents on the heart and blood circulation].

In 47 patients ECG tracings were recorded and cardiovascular values determined before therapy, during treatment with antidepressive agents after it had been in progress for at least 3 weeks, and 4 weeks after withdrawal of therapy. In a further 19 patients in whom antidepressive therapy could not be withdrawn, the same test battery was repeated after an average period of 13 months. No serious disturbances of cardiac rhythm were detected and certain changes in ECG criteria (prolongation of PR interval, widening of QRS complex, prolongation of QTc time and T-wave flattening) proved to be reversible. There was no difference between tricyclic and tetracyclic antidepressive agents. We are nevertheless of the opinion that ECG and cardiac function should be carefully monitored in elderly patients and in those on prolonged therapy with high doses of antidepressives. The results of this study are discussed and compared with previously published findings.

Adolescent↗

PubMed2026

Whole-exome Sequencing Identifies Novel Candidate PCNT Variants in a Child With Overlapping MOPD II Features: A Case Report.

A 7-year-old Chinese boy presented with severe postnatal growth failure (height <3rd percentile at age 7 years), global developmental delay, moderate intellectual disability, and characteristic dysmorphic features including hypertelorism, short palpebral fissures, low-set ears, and a broad nasal bridge. A single electrocardiogram demonstrated a borderline corrected QT interval (QTc = 450 ms). No arrhythmias, QT-prolonging medications, electrolyte abnormalities, or relevant family cardiac history were identified. This finding warrants longitudinal cardiology follow-up and should not be interpreted as definitive Long QT syndrome. Whole-exome sequencing identified two novel missense variants in the PCNT gene (NM_006031.5): c.5675A>G (p.Glu1892Gly) in exon 28 and c.9734G>T (p.Arg3245Ile) in exon 45. Both variants were absent from gnomAD, ExAC, the 1000 Genomes Project database, and Chinese population databases, fulfilling ACMG criterion PM2. Although classified as variants of uncertain significance (VUS) because of limited functional evidence and conflicting in silico predictions, the variants occur in a gene associated with primordial dwarfism and are accompanied by partial phenotypic overlap with Microcephalic Osteodysplastic Primordial Dwarfism Type II (MOPD II). However, parental segregation analysis was unavailable; therefore, the variant phase could not be confirmed, and a recessive disease mechanism could not be established. These findings support the presence of candidate PCNT variants in an atypical primordial dwarfism phenotype and illustrate the utility of whole-exome sequencing for generating testable molecular hypotheses in genetically heterogeneous growth disorders. A definitive molecular diagnosis cannot be established at present, and the isolated borderline QTc finding requires further clinical evaluation.

Humans↗

PubMed1978

[Hemodynamic effects of disopyramide and procainamide in open-chest animals].

Hemodynamic effects of two antiarrhythmic agents, disopyramide and procainamide, have been evaluated in anesthetized open-chest healthy pigs after random administration. At therapeutic plasma concentrations none of these agents proved to have deleterious hemodynamic effects. The most important action was observed after disopyramide infusion and consisted in significant bradycardia which confirmed the known effect on sinus node automaticity of the drug. Left ventricular dp/dt, an index of cardiac contractility, was unchanged after infusion of both drugs. On the ECG intervals, only procainamide provoked a significant prolongation of QTc. It is concluded that at therapeutic dosage disopyramide does not present deleterious hemodynamic effects in animals and proves to be a valid alternative to other traditional antiarrhythmic agents.

Animals↗

PubMed1979

Pharmacokinetics of verapamil in man.

Verapamil was given intravenously (10 mg) and orally (120 mg) in six healthy subjects. After intravenous administration, the serum levels in all subjects declined bi-exponentially. Thereupon, pharmacokinetic parameters were calculated using a two-compartment open model. The half-lives of distribution (T 1/2 alpha) and elimination (T 1/2 beta) phases showed 0.23 hour and 4.21 hour on an average respectively. The apparent volume of distribution [Vd (area)] showed 2.51 1/kg and body clearance (C1b) showed 500.64 ml/min on an average. Renal clearance was smaller than normal human creatinine clearance. After oral administration, the time to reach peak blood level (Tmax) was reached within 1.84 hour and the peak serum concentration showed 219.09 ng/ml on an average. The bioavailability was only 22.47% on an average. Verapamil produced a marked prolongation of PQ interval on electrocardiogram and the degree of PQ interval prolongation was closely related to the increase in serum concentration of this compound. QRS, QTc and RR interval were not changed by this compound.

Administration, Oral↗

PubMed1979

The electrocardiographic and antiarrhythmic effects of imipramine hydrochloride at therapeutic plasma concentrations.

The electrocardiographic effects of imipramine hydrochloride at therapeutic plasma concentrations were determined in 44 depressed patients during a 6-week clinical outcome study of depression. During each week of the protocol, i.e., 2 weeks of control and 4 weeks of drug treatment, a standard 12-lead ECG, high-speed, high-fidelity ECG tracings, and a 24-hour continuous ECG recording were obtained. PR, QRS, and QTc intervals, T-wave amplitude, heart rate and frequency of ventricular premature depolarizations (VPDs) were measured. The plasma concentration of imipramine and desmethylimipramine was measured three times a week. Imipramine prolonged the PR (p less than 0.001), QRS (p less than 0.001) and QTc (p less than 0.001) intervals, increased the heart rate (p less than 0.001) and lowered T-wave amplitude (p less than 0.05) during the 4 weeks of treatment. No patient developed high-grade atrioventricular block or severe intraventricular conduction abnormalities. In addition, imipramine had a potent antiarrhythmic action in patients who were recovering from depression. Ten of 11 patients who had more than 10 VPDs/hour had 90% or greater arrhythmia suppression during antidepressant treatment with imipramine at plasma concentrations ranging from 100--302 ng/ml.

Adult↗