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Biomedical subjects

L Toivonen

Publications and source records attributed to L Toivonen.

At least 55 records · Page 3Linked to original sources
PubMed1996

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.min-1. Group mean total QT and early QT exhibited better linear correlations with heart rate (r 0.998 and 0.999) than with cardiac cycle length (r 0.954 and 0.959). The slope relating total QT to heart rate was -1.30 during exercise and -1.42 during recovery (P < 0.05). The corresponding slopes relating early QT to heart rate were -1.11 and -1.30 (P < 0.05). Late QT, as a proportion of total QT, increased at high heart rates. Rate correction using Bazett's method gave abnormal total QT values (> 440 ms) in 12 children (67%) whereas linear correction gave values below 440 ms only. In conclusion, the relationship between QT and heart rate is linear and differs during exercise and recovery. Inhomogeneity of repolarization increases at high heart rates. Linear correction of total QT and early QT intervals improves the evaluation of repolarization duration in exercise testing in children.

Adolescent↗
PubMed1996

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. METHODS: HRV and its circadian variation were studied in 12 diabetic and 11 non-diabetic renal transplantation and in 12 control patients. HRV in time and frequency domains was determined from 24-hour ECG recordings. RESULTS: In the diabetic group, all time domain and frequency domain measures of HRV were markedly reduced (P < 0.05), when compared with the control group, and the circadian variation of HRV was absent. The mean (SD) amplitudes (ms) in the frequency bands were: high frequency: 3 (1), 6 (3) and 15 (3); low frequency: 9 (7), 16 (10) and 25 (8); very low frequency: 14 (8), 23 (12) and 30 (11) in the diabetic and non-diabetic uraemic and in the control patients, respectively. In non-diabetic uraemic patients, a tendency to reduced HRV was observed, but no statistical differences in HRV measures were found when compared with the control group. CONCLUSION: The severe impairment of HRV in patients with end-stage diabetic nephropathy is probably due to autonomic neuropathy and partly also to the co-existing heart diseases. It may be a contributing risk factor for ventricular arrhythmias and sudden death in these patients. Uraemia alone causes similar but less severe changes in HRV.

Adult↗
PubMed1996

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. The group mean amplitudes of the atrial signal were equal in all postures, and comparable to the supine value (1.01 +/- 0.51 mV). However, the values within each individual varied considerably according to position, by a range of 0.46 +/- 0.41 mV on average. Testing only supine did not always predict decent sensing when upright, e.g., in 3 patients the atrial signal decreased more than 0.5 mV. In 24-hour ambulatory electrocardiography, with the sensitivity (0.15-0.30 mV) set to cover all postures, atrial beats were undersensed not at all in 4 patients, < 0.01% in 6 patients, and < 0.1% in the remaining 6 patients. Thus, with a floating atrial electrode, sensitivity testing in various postures is advisable to ascertain proper sensing function.

Aged↗
PubMed1996

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. PATIENTS: 20 patients with stable exertional angina and > or = 50% luminal diameter narrowing of at least one major coronary artery. INTERVENTIONS: Each patient was studied on two separate days, once after administration of 1.25 g of ethanol per kilogram of body weight diluted to 15% in juice, and once after an equivalent volume of juice; both tests were in the evening and lasted 90 minutes. The patients were scheduled to have 8 periods of walking for 10 min according to a time table. An ambulatory electrocardiogram and the occurrence of anginal attacks were recorded and blood pressure and blood ethanol concentration were measured until the next morning. RESULTS: The blood ethanol concentration (mean (SD)) rose to 28.8 mmol/l (1.3 (0.4)/1000). Alcohol raised the systolic blood pressure from 132 (16) to 141 (14) mm Hg (P < 0.05 compared with juice). The mean heart rate increased from 57 (7) to 64 (8) beats/min (P < 0.05) for 13 hours after ethanol ingestion compared with juice. The total duration of ischaemia during the ethanol test was 3.5 (median, range 0-80) min, compared with 0 (range 0-67) min for the juice test (P < 0.05). The difference resulted mainly from more silent ischaemia after ethanol ingestion (2.3 (0-80) v 0 (0-67) min; P < 0.05). The ST segment depression time integral increased during the ethanol test (4.4 (0-170) mm x min) relative to that during the juice test (0 (0-103) mm x min; P < 0.01) and especially during the following 13 hours after alcohol (3.5 (0-123) mm x min) compared with juice (0 (0-67) mm x min; P < 0.005). There were no changes in the number, duration, or ST segment depression time integral of the episodes of symptomatic angina, indicating that ethanol augmented the appearance of silent ischaemia. CONCLUSIONS: Acute heavy ethanol drinking aggravates myocardial ischaemia in patients with stable angina pectoris.

Adult↗
PubMed1995

Linkage of the long QT syndrome to the short arm of chromosome 11: use of five highly polymorphic markers towards more detailed localization of the mutant gene.

The long QT syndrome is an autosomally dominantly inherited cardiac disorder characterized by abnormalities of myocardial repolarization, exercise- or stress-related syncopal attacks and risk of sudden death due to cardiac arrhythmias. Genetic linkage studies have defined three LQT loci on chromosomes 11p15.5, 3q21-24 and 7p35-36. We performed linkage analyses in three Finnish LQT families using five amplifiable markers assigned to chromosome 11p15. By multipoint linkage analyses we obtained a maximal lod score of 5.503, suggesting that the LQT1 locus maps between D11S922 and D11S1338 on chromosome 11. Our data provide a step towards closer definition of the exact borderlines of the LQT1 locus in chromosome 11 and demonstrate markers with high utility in identification of gene carriers in the affected families.

Adolescent↗
PubMed1995

Reversal of autonomic derangements by physical training in chronic heart failure assessed by heart rate variability.

Decreased heart rate variability has been associated with chronic congestive heart failure (CHF). We evaluated the effect of physical training on heart rate variability in 20 patients with CHF (NYHA class II-III) randomized to training (n = 8) and control (n = 12) groups. The training group underwent 3 months of physical training, by exercising on a bicycle ergometer for 30 min three times a week at a load corresponding to 50-60% of their peak oxygen consumption. Heart rate variability was assessed from 20-h ambulatory ECG recordings in the frequency domain, determined by high (0.15-0.40 Hz), low (0.04-0.15 Hz) and very low frequency (0.008-0.04 Hz) components. The high frequency component increased by 22-55% in the training group during the day (P = 0.0001) but not at night. The increase was seen during both sedentary and active periods. The low frequency/high frequency ratio attenuated in the training group during the day (P = 0.05) whereas an increase was seen in the control group throughout the day (P = 0.0003). Training lengthened the exercise duration by 71% at a submaximal workload (P = 0.01) and tended to increase the peak oxygen consumption by 15% (P = 0.09). These remained unchanged in the control group. In conclusion, physical training, which improves exercise capacity, ameliorates the autonomic derangement in CHF by increasing the parasympathetically mediated component of heart rate variability. It may thus influence favourably the prognosis of the disease.

Adult↗
PubMed1995

Father's heart beat responds to the birth of his child.

We monitored the electrocardiogram of 20 fathers while their child was born. Paternal heart rate rose on average by 53% during delivery from the starting point frequency (72 beats/min.) to the maximum (115 beats/min.) just before the birth of the child. Judging from the heart rate variation, paternal sympathetic activity increased by 25% and vagal tone decreased by 22% during delivery. No derangements in cardiac function were encountered, not even in the man who fainted.

Adult↗
PubMed1994

Provocation of ventricular tachycardia by antimalarial drug halofantrine in congenital long QT syndrome.

This report deals with two patients who suffered sustained episodes of torsade de pointes ventricular tachycardia while using the novel antimalarial drug halofantrine. Both patients had congenital long QT syndrome, and their QT interval was further prolonged at the time of the event. This first electrocardiographic documentation of ventricular arrhythmias together with halofantrine's known prolonging effect on the QT interval demonstrates that the drug has the potential to induce life-threatening arrhythmias.

Adolescent↗
PubMed1994

High-resolution and signal-averaged electrocardiography to separate post-myocardial infarction patients with and without ventricular tachycardia.

High-resolution and signal-averaged ECG, 24 h Holter recording and ejection fraction were used to separate post-myocardial infarction patients with and without ventricular tachycardia (VT) among 150 individuals: 26 patients with an old myocardial infarction and documented sustained VT, 104 patients with an acute myocardial infarction without sustained VT, who were followed-up for 2 years, and 20 healthy volunteers. Bipolar orthogonal XYZ leads were recorded, high-pass filtered at cut-off frequencies of 25, 40, 60, 80 and 100 Hz, and combined to vector magnitude square root of X2 + Y2 + Z2. The filtered QRS duration, the root-mean-square voltages of different time intervals and the durations of low amplitude signals under different thresholds, both from the initial and terminal QRS, were calculated. The sensitivity and specificity of each parameter alone and in every combination of two, three and four parameters (17 million different combinations) were computed both from non-averaged and averaged data. The best separation was achieved by 12 combinations all including four signal-averaged ECG parameters, with a sensitivity of 81% and a specificity of 79%. The parameters represented most were: filtered QRS duration at 25 Hz, RMS voltage of the last 50 ms at 25 Hz, terminal LAS duration at 80 Hz, and RMS voltage of the last 20 ms at 80 Hz. Parameters of the initial QRS complex did not improve either the sensitivity or the specificity of the method. In logistic regression analysis, the best combinations of four signal-averaged ECG parameters separated VT patients better (P < 0.001) than non-sustained ventricular tachycardia at Holter (P = 0.001); left ventricular ejection fraction (P = 0.01); or age (P = 0.006). Parameters calculated from averaged data gave better results than parameters calculated from non-averaged data.

Adult↗
PubMed1994

Arrhythmias and ST segment deviation during prolonged exhaustive exercise (ski marathon) in healthy middle-aged men.

To evaluate the occurrence of arrhythmias and silent ischaemia during a prolonged exhaustive exercise in cold climate conditions, we monitored 37 healthy middle-aged men (age 40-56 years) who were randomly selected from participants of a ski marathon. Completing the 75-90 km race took 7-12 h. The highest and lowest mean hourly heart rates during skiing were 150 +/- 9 (mean +/- SD) and 138 +/- 11 beats.min-1. The maximum heart rate was 161 +/- 9 beats.min-1, and occurred in most skiers during the first hour. Ventricular premature complexes (VPCs) were present in 33 of 37 men (89%) with a median frequency of five beats during skiing (range 0-425). Complex forms occurred in eight men (22%), and atrial ectopics appeared in 33 of 35 participants (94%). The frequency of the arrhythmias did not increase over the skiing period. At control monitoring during a representative period the highest mean hourly heart rate was 74 +/- 12 beats.min-1 and VPCs were seen in 21 men (57%) at a median frequency of one beat during the control period (range 0-338) and complex forms occurred in three men (8%). Three men had asymptomatic ST segment depression of 0.2-0.3 mV lasting 2-10 min during the first hour of skiing. One of them had marginal ST segment depression (0.1 mV) at exercise electrocardiography, but all had normal results at exercise thallium scintigraphy and echocardiography. Thus, arrhythmias were significantly (P < 0.001) increased in middle-aged men during exhaustive prolonged exercise as compared to those observed during a similar period of time of normal daily life.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Influence of acute alpha 1-adrenergic antagonism on heart rate variability in patients with old myocardial infarction.

Decreased heart rate (HR) variation is a predictor of cardiac and arrhythmic death after myocardial infarction (MI). The present study examined the influence of alpha-adrenergic system on HR variation (HRV). A novel alpha 1-adrenergic antagonist, abanoquil (UK 52,046) was administered acutely to 27 patients with old MI in random placebo-controlled cross-over design. Abanoquil decreased mean sinus interval for 24 h from 884 +/- 119 (mean +/- SD) to 830 +/- 116 ms (p = 0.0001). The total spectral (0.01-1.0 Hz) amplitude in HRV decreased from 44.6 +/- 14.8 to 40.6 +/- 14.8 ms (p = 0.018). Corresponding decreases were from 28.3 +/- 10.6 to 25.3 +/- 10.8 ms (p = 0.011) in the low-frequency band (0.04-0.15 Hz) and from 13.8 +/- 6.6 to 12.1 +/- 6.1 ms (p = 0.055) in the high-frequency band (0.15-0.40 Hz). Changes of similar magnitude were observed during active and sleep time. All changes in HRV were related by covariate analysis to the decrease in sinus interval and were not associated with an orthostatic decrease in blood pressure (BP) induced by abanoquil. The dominant effect of acute alpha 1-adrenergic antagonism appears to be a decrease in parasympathetic activity, although it may also stabilize sympathetic control of the heart. Thus, the autonomic nervous modification caused by alpha-adrenoceptor antagonists might be disadvantageous in treatment of patients at high risk of fatal cardiac events.

Adrenergic alpha-1 Receptor Antagonists↗