Bioelectromagnetic localization of a pacing catheter in the heart.

The accuracy of localizing source currents within the human heart by non-invasive magneto- and electrocardiographic methods was investigated in 10 patients. A non-magnetic stimulation catheter inside the heart served as a reference current source. Biplane fluoroscopic imaging with lead ball markers was used to record the catheter position.

Changes in heart rate variability in elderly patients undergoing major noncardiac surgery under spinal or general anesthesia.

Background And Objectives: Heart rate variability (HRV), widely used as an indicator of activity of the autonomic nervous system, has been reported to decrease during and after both spinal and general anesthesia in patients without cardiovascular disease. We evaluated the changes in HRV bands in 40 patients with a high risk of ischemic heart disease.

Methods: The patients were randomly assigned to receive either spinal (SA) or general anesthesia (GA) for elective total hip arthroplasty or peripheral vascular surgery.

Sinus node function and ventricular repolarization during exercise stress test in long QT syndrome patients with KvLQT1 and HERG potassium channel defects.

Objectives: This study was performed to evaluate the QT interval and heart rate responses to exercise and recovery in gene and mutation type-specific subgroups of long QT syndrome (LQTS) patients.

Background: Reduced heart rate and repolarization abnormalities are encountered among long QT syndrome (LQTS) patients. The most common types of LQTS are LQT1 and LQT2.

Nonfluoroscopic localization of an amagnetic stimulation catheter by multichannel magnetocardiography.

This study was performed to: (1) evaluate the accuracy of noninvasive magnetocardiographic (MCG) localization of an amagnetic stimulation catheter; (2) validate the feasibility of this multipurpose catheter; and (3) study the characteristics of cardiac evoked fields. A stimulation catheter specially designed to produce no magnetic disturbances was inserted into the heart of five patients after routine electrophysiological studies. The catheter position was documented on biplane cine x-ray images.

Decreases by magnesium of QT dispersion and ventricular arrhythmias in patients with acute myocardial infarction.

Aims: Magnesium treatment suppresses ventricular arrhythmias in acute myocardial infarction and possibly mortality after infarction, but the underlying mechanisms are inadequately understood. We tested whether the effect of magnesium could be attributed to an influence on the autonomic control of the heart, changes in disturbed repolarization, relief of ischaemia or limitation of myocardial injury.

Methods And Results: Fifty-nine consecutive patients with acute myocardial infarction were randomized to receive 70 mmol of magnesium (n = 31) infused over 24 h or placebo (n = 26).

Electrocardiographic measures of ventricular repolarisation dispersion in patients with coronary artery disease susceptible to ventricular fibrillation.

Objective: To study electrocardiographic measures of ventricular repolarisation dispersion in patients prone to ventricular fibrillation compared with controls matched for the extent of coronary heart disease and the use of beta blockers.

Design: A case-control study.

Setting: Cardiovascular laboratory of a tertiary referral centre.

Magnetocardiographic pacemapping for nonfluoroscopic localization of intracardiac electrophysiology catheters.

The purpose of the study was to validate, in patients, the accuracy of magnetocardiography (MCG) for three-dimensional localization of an amagnetic catheter (AC) for multiple monophasic action potential (MAP) with a spatial resolution of 4 mm2. The AC was inserted in five patients after routine electrophysiological study. Four MAPs were simultaneously recorded to monitor the stability of endocardial contact of the AC during the MCG localization.

Magnetocardiographic QT interval dispersion in postmyocardial infarction patients with sustained ventricular tachycardia: validation of automated QT measurements.

QT dispersion is a measure of heterogeneity in ventricular repolarization. Increased ECG QT dispersion is associated with life-threatening ventricular arrhythmias. We studied if magnetocardiographic (MCG) measures of QT dispersion can separate postmyocardial infarction patients with and without susceptibility to sustained VT.

Extensive variation in the signal amplitude of the atrial floating VDD pacing electrode.

The dependence of atrial signal amplitude on the site of the atrial sensing dipole of a single-pass lead was examined in 29 patients. The vertical location of the dipole was documented in supine fluoroscopy during quiescent and deep breathing and in upright chest roentgenogram, and was expressed as a proportion of the right atrial height. As the group average, the atrial signal amplitude was equal when tested in supine, sitting, standing, and right- or left-side positions in follow-up determinations.

Effect of ethanol drinking, hangover, and exercise on adrenergic activity and heart rate variability in patients with a history of alcohol-induced atrial fibrillation.

To elucidate the mechanism of alcohol-induced atrial fibrillation (AF) we studied the heart rate variability and parameters of the adrenergic system during alcohol intake, hangover, and exercise in 6 men (mean age 43 years) prone to alcohol-induced AF, together with 6 age-matched controls. The ambulatory (15 hour) electrocardiogram was recorded and blood samples were taken for lymphocytic beta adrenoceptor, plasma catecholamine, and cyclic adenosine monophosphate (cAMP) measurements before and after alcohol intake (blood alcohol 1.5 per thousand), during hangover, and after a standardized bicycle exercise test.

Evaluation of QT interval duration and dispersion and proposed clinical criteria in diagnosis of long QT syndrome in patients with a genetically uniform type of LQT1.

Objectives: This study investigated the ability of QT duration, QT dispersion (QTD) and clinical diagnostic criteria to correctly identify genetically documented LQT1 type long QT syndrome (LQTS) patients, and to separate symptomatic and asymptomatic LQT1 patients.

Background: Ventricular repolarization has played an essential role both in diagnosis and risk assessment of LQTS. Today, molecular genetic techniques permit unequivocal identification of many LQTS patients.

Autonomic modulation of QT intervals in post-myocardial infarction patients with and without ventricular fibrillation.

The autonomic nervous system plays an important role in the genesis of sudden cardiac death. The aim of this study was to evaluate spatial autonomic QT interval modulation at the myocardial level. Circadian patterns of QT intervals and heart rate variability (HRV) components and their hourly linear correlations were determined by Holter recordings in 15 healthy subjects (controls), in 15 post-myocardial infarction (MI) patients resuscitated from ventricular fibrillation (VF) (VF group), and in 15 matched infarction patients without a history of arrhythmia events (MI group).

Effects of epinephrine and phenylephrine on QT interval dispersion in congenital long QT syndrome.

Objectives: Measurement of QT interval dispersion during pharmacologic adrenergic stimulation was used to assess the effect of alpha- and beta-adrenergic stimulation on arrhythmic vulnerability in familial long QT syndrome (LQTS).

Background: Nonhomogeneity in the ventricular action potential duration causes electrical instability leading to life-threatening ventricular arrhythmias and is markedly increased in LQTS. QT interval dispersion measured from the electrocardiogram (ECG) can be used as an index of nonhomogeneous ventricular repolarization.

Rate adaptation of QT intervals during and after exercise in children with congenital long QT syndrome.

Objectives: To improve the diagnostic criteria of the congenital long QT syndrome in borderline cases we examined rate adaptation of ventricular repolarization phases during exercise and subsequent recovery in children with the long QT syndrome and controls.

Methods: Nineteen children with definite long QT syndrome and 19 healthy controls underwent exercise testing. QT intervals were measured to the apex (early QT), to the end (total QT) and from apex to the end of the T wave (late QT) at heart rates from 90 by steps of 10 to 150 beats, min-1.

Dispersions of the QT interval in postmyocardial infarction patients presenting with ventricular tachycardia or with ventricular fibrillation.

Increased QT interval dispersion is associated with ventricular arrhythmias. The aim of this study was to examine if in postmyocardial infarction patients with impaired left ventricular function, increased QT dispersion is associated with ventricular tachycardia (VT) and ventricular fibrillation (VF). Measures of QT dispersion, calculated as maximum-minimum (D) and standard deviation (SD) of QTend, QTapex, JTend, JTapex, and Tend intervals in the 12-lead electrocardiogram, were compared in patients who late after myocardial infarction experienced sustained VT (VT group) only, VF (VF group) only, or had no ventricular arrhythmias (controls).

Molecular genetics of the long QT syndrome: two novel mutations of the KVLQT1 gene and phenotypic expression of the mutant gene in a large kindred.

At least three different gene loci were recently shown to account for the long QT syndrome (LQTS), a monogenic disorder with altered myocardial repolarization and occurrence of life-threatening cardiac arrhythmias. We screened 44 unrelated probands for mutations of the gene encoding the cardiac potassium channel KVLQT1 using single-strand conformational polymorphism (SSCP) and subsequent DNA sequencing. Two different mutations, T182I and D188N, were identified in two separate pedigrees.

Comparison of sotalol and metoprolol in the prevention of atrial fibrillation after coronary artery bypass surgery.

New-onset atrial fibrillation (AF) is frequent after coronary artery bypass grafting (CABG), and beta-blockers decrease its incidence. To examine whether a beta-blocker with class III properties is superior to a pure one, 191 consecutive patients undergoing CABG were randomized to receive oral sotalol, 120 mg daily (n = 93), or metoprolol, 75 mg daily (n = 98), postoperatively. The doses were adjusted if beta-blockade was inadequate or excessive.

Cardiac repolarization interval in end-stage diabetic and nondiabetic renal disease.

Background And Hypothesis: QT interval length is influenced by autonomic nervous activity. In patients with diabetic autonomic neuropathy, both prolongation and shortening of ventricular repolarization has been reported. We studied diabetic and nondiabetic uremic patients to assess the effects of autonomic neuropathy on QT interval length.

Electrocardiographic repolarization during stress from awakening on alarm call.

Objectives: The present study aimed to characterize the electrocardiographic features of cardiac repolarization during an arousal reaction in healthy subjects.

Background: Electrocardiographic ST segments and T waves may indicate the activity of cardiac autonomic nervous control. Abnormal dynamics of repolarization are considered to reveal susceptibility to cardiac arrhythmias.

Abnormal ambulatory electrocardiographic findings in patients with the Marfan syndrome.

Objectives: The aim of this study was to assess the prevalence of cardiac dysrhythmias and abnormalities of conduction and repolarization in the Marfan-syndrome (MFS).

Subjects And Methods: Forty-five adult MFS patients (25 men) and healthy age and sex matched controls. A 24-h ambulatory electrocardiogram was recorded.

Dynamics of the QT interval during and after exercise in healthy children.

The dynamics and homogeneity of the QT interval have been used as indicators of susceptibility to ventricular arrhythmias. We determined the relationship between QT intervals and heart rate during exercise testing and subsequent recovery in 18 healthy children. The QT intervals were measured to the apex (early QT), to the end (total QT), and from the apex to the end of the T wave (late QT) (inhomogeneity of repolarization) at heart rates from 60 by steps of 10 to 180 beats.

Heart rate variability in diabetic and non-diabetic renal transplant patients.

Background: Heart rate variability (HRV) has been used to investigate the autonomic modulation of heart rate. Diminished HRV has been observed in diabetic autonomic neuropathy, a condition associated with increased mortality. Uraemia is associated with impaired autonomic function, but reports on the effects of uraemia on HRV are scarce.

Acute heavy alcohol intake increases silent myocardial ischaemia in patients with stable angina pectoris.

Objective: To evaluate the effect of acute alcohol ingestion on myocardial ischaemia in patients with coronary heart disease and stable angina.

Design: Randomised crossover study using fruit juice with and without ethanol.

Setting: Division of cardiology in a university hospital.

Dependence of atrial sensing function on posture in a single-lead atrial triggered ventricular (VDD) pacemaker.

The influence of body posture on atrial sensing was examined in a single-lead VDD pacemaker in 16 patients. At implantation, a position was searched for the floating atrial bipolar sensor to obtain an adequate atrial signal amplitude. After 1-12 months the atrial signals were measured by programming the sensitivity in five postures: supine, sitting, and standing and lying on the right and left sides.