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Biomedical subjects

K I Lie

Publications and source records attributed to K I Lie.

At least 217 records · Page 12Linked to original sources

Electrocardiographic patterns relative to initiating mechanisms of exercise-induced ventricular tachycardia.

The initiating mechanisms of exercise-induced ventricular tachycardia were studied in a population of 5842 patients who performed 9064 bicycle exercise tests. Sixty (1%) patients had 194 episodes of ventricular tachycardia during the test. Forty-two percent of these occurred during exercise and 58% during recovery. Two different initiating electrocardiographic patterns were observed. In 17 (28%) patients ventricular tachycardia was initiated by a short-long-short sequence of R-R intervals (group 1). Thirty-eight (63%) patients did not have this pattern of interval changes preceding ventricular tachycardia (group 2). Five (8%) other patients showed both patterns. The clinical characteristics of the groups were different for angina and cardiomyopathy but not for previous myocardial infarction. In group 1 ventricular tachycardia was related to recovery (76%; p < 0.05). In group 2 tachycardia occurrence was equally divided between exercise and recovery. The electrocardiographic differences suggest that different initiating mechanisms are involved in the development of exercise-induced ventricular tachycardia. The present findings may enhance aimed drug therapy in ventricular tachycardia.

Electrocardiography↗

Late onset atrioventricular nodal tachycardia.

AV nodal tachycardia may present at any age, but onset in late adulthood is considered uncommon. To evaluate whether onset of AV nodal tachycardias at older age is related to organic heart disease (possibly setting the stage for re-entry due to degenerative structural changes) 32 consecutive patients with symptomatic AV nodal tachycardia were studied. The age at onset of attacks showed a bimodal pattern, with 2 peaks: one between 15 and 35 years (22 patients) and one around 55 years (10 patients). Significantly more older patients had an underlying heart disease (60% versus 14%, P < 0.01), with coronary artery disease in 4 and hypertensive heart disease in 3. Frequent supraventricular ectopic activity was seen during baseline 24-h ambulatory monitoring in all the older patients, versus in only half of the younger patients (P = 0.005). These results indicate that late onset AV nodal tachycardia (i.e. > age 45 years) is not infrequent (33%). The frequent supraventricular arrhythmias on one hand and age-related structural AV nodal changes, potentially enhanced by underlying heart disease on the other, both may contribute to the development of late onset re-entrant AV nodal tachycardia.

Adult↗

Culprit lesion morphology and stenosis severity in the prediction of reocclusion after coronary thrombolysis: angiographic results of the APRICOT study. Antithrombotics in the Prevention of Reocclusion in Coronary Thrombolysis.

OBJECTIVES: In the APRICOT study (Antithrombotics in the Prevention of Reocclusion In Coronary Thrombolysis), we sought to determine whether angiographic characteristics of the culprit lesion could predict reocclusion after successful thrombolysis and to analyze the influence of three antithrombotic treatment regimens. BACKGROUND: After successful thrombolysis, reocclusion is a major problem. Prediction of reocclusion by angiographic data and choice of antithrombotic treatment would be important for clinical management. METHODS: After thrombolysis, patients were treated with intravenous heparin until initial angiography was performed within 48 h. Patients with a patent infarct-related artery were eligible. Three hundred patients were randomly selected for treatment with coumadin, aspirin (300 mg once daily) or placebo. Patency on a second angiographic study after 3 months was the primary end point of the study. RESULTS: Reocclusion rate was 25% with aspirin, 30% with coumadin and 32% with placebo (p = NS). Lesions with > 90% stenosis reoccluded more frequently (42%) than did those with < 90% stenosis (23%) (p < 0.01). Reocclusion rate of smooth lesions was higher (34%) than that of complex lesions (23%) (p < 0.05). In lesions with < 90% stenosis, the reocclusion rate was lower with aspirin (17%) than with coumadin (25%) or placebo (30%) (p < 0.01). In complex lesions, the reocclusion rate was lower with aspirin (14%) than with coumadin (32%) or placebo (25%) (p < 0.02). Multivariate analysis showed only stenosis severity > 90% to be an independent predictor of reocclusion (odds ratio 2.31, 95% confidence interval 1.28 to 4.18, p = 0.006). CONCLUSIONS: Angiographic features of the culprit lesion after successful coronary thrombolysis significantly predict the risk of reocclusion: high grade (> 90%) stenoses reoccluded more frequently. Aspirin was effective only in complex and less severe lesions (< 90% stenosis). These findings should prompt investigation of the effects of an aggressive approach to patients with severe residual stenosis.

Aspirin↗

Endothelium dependent relaxation in two different models of chronic heart failure and the effect of ibopamine.

OBJECTIVES: The purpose was to relate endothelium dependent relaxation to neurohumoral and haemodynamic changes in rats with chronic heart failure. METHODS: Rats were submitted to either coronary ligation causing myocardial infarction or banding of the abdominal aorta (aortic stenosis), and comparisons were made with normal rats (n = 20 per group). Starting six weeks after surgery, half of the experimental animals received ibopamine and the other half served as controls and were given saline for another three weeks. After this, haemodynamic and neurohumoral variables were determined and the rats were killed. Rings of both the thoracic and abdominal aorta were studied in organ baths to measure their response to vasoactive agents. RESULTS: Increased plasma noradrenaline concentrations in rats with myocardial infarction and aortic stenosis were reduced by ibopamine. Blood pressure and heart rate, which were higher in rats with aortic stenosis than in rats with myocardial infarction and in normal rats, were unaffected by ibopamine. The maximal relaxation to sodium nitrite was depressed in the thoracic aorta from rats with myocardial infarction. The pIC50 of metacholine induced relaxation was smaller in the thoracic aorta from rats with myocardial infarction and aortic stenosis. By contrast, both pIC50 and the maximal relaxation (Emax) were increased in the abdominal aorta from rats with aortic stenosis, whereas Emax was smaller in rats with myocardial infarction. Ibopamine had no significant effects on these responses. CONCLUSIONS: Endothelium dependent relaxation to metacholine was selectively altered in rats with chronic heart failure due to aortic stenosis, probably because of differences in regional haemodynamics. In rats with myocardial infarction, however, endothelium dependent relaxation was impaired in both the thoracic and abdominal aorta. Ibopamine acted as a neurohumoral modulator by reducing increased noradrenaline concentrations but had no significant effect on either endothelium dependent or independent relaxation.

Animals↗

Electrophysiologic and pharmacokinetic profile of the new antiarrhythmic drug TYB-3823 in humans.

In an open-label study, electrophysiology and pharmacokinetics of TYB-3823, a new antiarrhythmic compound, were investigated. Sixteen patients underwent an electrophysiologic study before and after intravenous (i.v.) administration of TYB-3823. Two patients each received the following increasing doses: 0.2, 0.4, 0.8, and 1 mg/kg. Eight patients received 1.2-mg/kg. TYB-3823 concentrations followed a biexponential decrease with a terminal half-life (t1/2) of 3.88 +/- 0.87 h. Clearance was 47.2 +/- 18.5 L/h, and volume of distribution was 250 +/- 77 L. Dose-dependent pharmacokinetics were evident. Significant effects of TYB-3823 were apparent at doses > or = 0.8 mg/kg (n = 12), including increase in the AH and HV interval from 92 +/- 17 to 105 +/- 19 ms (p < 0.002) and 47 +/- 7 to 60 +/- 12 ms (p < 0.005), respectively. QRS duration was prolonged from 100 +/- 16 to 126 +/- 22 ms (p < 0.001), accompanied by an increase of the corrected QT interval from 425 +/- 28 to 465 +/- 37 ms (p < 0.002). The corrected JT interval remained unchanged, however, refractoriness did not change, but monophasic action potential duration (APD) tended to decrease. TYB-3823 appeared effective against reinduction of all arrhythmias observed during the control study [atrial fibrillation, atrioventricular (AV) nodal tachycardias]. TYB-3823 depresses conduction velocity significantly without prolonging refractoriness. Therefore, TYB-3823 may be classified as a class 1C antiarrhythmic. On the basis of the present results, additional class 1B activity cannot be excluded. TYB-3823 has antiarrhythmic properties, appears to be devoid of proarrhythmic effects, and is well tolerated.

Action Potentials↗

Sustained atrial flutter around the tricuspid valve in pigs: differentiation of procainamide (class IA) from flecainide (class IC) and their rate-dependent effects.

The wavelength theory considers two determinants of reentry, i.e., refractoriness and conduction velocity. It does not take excitability into account primarily. We evaluated frequency-dependence of excitability and refractoriness before and after flecainide or procainamide administration in relation to termination of reentrant atrial flutter. After making a Y-shaped lesion in the right atrium, we induced 62 flutters (cycle length 171 +/- 15 ms) by electrical stimulation in 15 pigs. Strength-interval curves were determined to assess excitability and refractoriness. Multiple cycle lengths were used to establish rate-dependent changes. Flutter cycle length increased after flecainide (to 290 +/- 67 ms) or procainamide (to 295 +/- 54 ms). The flutters always terminated abruptly (flecainide dose 103 +/- 104 mg, plasma concentration 370 +/- 21 ng/ml; procainamide dose 1,150 +/- 686 mg, concentration 51 +/- 24 mg/l). Flecainide caused an increase in diastolic thresholds from 0.3 +/- 0.2 to 0.8 +/- 0.5 mA (p < 0.006) and procainamide from 0.5 +/- 0.3 to 0.9 +/- 0.5 mA (p < 0.02). The increase in threshold was frequently dependent. Procainamide increased refractoriness at longer cycle lengths (> or = 250 ms), but this effect was abolished at shorter cycle lengths, indicating that only after significant slowing of the rate, prolongation of refractoriness may appear. Thus, both drugs interrupt reentrant flutter mainly by reducing excitability. Subclassification into IA and IC may be less relevant at high rates. Construction of strength-interval curves and assessment of rate-dependent "postrepolarization refractoriness" should be considered when one studies drugs that influence excitability.

Animals↗

Influence of intravenous diltiazem on left ventricular function in patients with severe coronary artery disease at rest and during pacing, monitored by computer-processed nuclear probe and tip-manometer data.

The influence of intravenous diltiazem on hemodynamics and left ventricular function indices was studied in 14 patients with severe coronary artery disease at rest and during atrial pacing. We used a tip manometer catheter for recording left ventricular pressure tracings and a nuclear probe for measuring left ventricular volume changes. Infusion of diltiazem at rest resulted in an increase in left ventricular enddiastolic volume (+16%, p < 0.0001); all other parameters did not differ significantly from baseline values. Angina pectoris occurred in all patients during atrial pacing before diltiazem infusion (ContrP); during pacing after diltiazem infusion (DiltP) only four patients became symptomatic (at the same pacing rates). Other differences between the two pacing studied and their baseline measurement were mean arterial pressure (ContrP: +13%, p < 0.001; DiltP: +11% p < 0.001), pulmonary wedge pressure (ContrP: +54%, p = 0.019; DiltP: NS), left ventricular enddiastolic pressure (ContrP: +40%, p < 0.005; DiltP: NS), left ventricular enddiastolic volume (ContrP: -19%, p = 0.001; DiltP: -33%, p = 0.0001), left ventricular ejection fraction (ContrP: -20%, p = 0.039; DiltP: NS), maximum rate of rise of left ventricular systolic pressure (ContrP: +22%, p = 0.001; DiltP: +20%, p = 0.03), time constant of relaxation (ContrP: +40%, p = 0.001; DiltP +8%, p = 0.047), stiffness constant of the diastolic pressure-volume relationship (ContrP: +157%, p = 0.0001; DiltP: +132%, p = 0.001), and left ventricular systolic work (ContrP: -35%, p = 0.0001; DiltP -46%, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Chronotropic response to exercise in patients with atrial fibrillation: relation to functional state.

OBJECTIVE: To determine the relation between functional capacity and heart rate response to exercise in patients with atrial fibrillation. SUBJECTS: 73 consecutive patients with chronic atrial fibrillation. MAIN OUTCOME MEASURES: Relation between functional capacity, measured as peak oxygen consumption (peak VO2; ml/min/kg), and heart rate at all stages of exercise in univariate and multivariate analyses. RESULTS: Peak VO2 showed no correlation with resting heart rate, but it showed a negative correlation with heart rate during the first stage of exercise (r = -0.94, p < 0.01). Indeed, heart rate during the early stages of exercise (stages 1-5) was higher in patients with a peak VO2 less than or equal to 20 ml/mm/kg than in those with a peak VO2 greater than 20 ml/min/kg (heart rate 140 v 125 beats/min, p < 0.05). At maximal exercise, however, peak VO2 was positively correlated with heart rate (r = 2.15, p < 0.0001). CONCLUSION: In patients with atrial fibrillation and impaired functional capacity heart rate at low levels of exercise is augmented but maximal heart rate attenuated compared with patients with preserved functional capacity. Excessive heart rate responses to minor exercise may have deleterious effects on left ventricular function and thereby further limit functional capacity.

Adrenergic beta-Antagonists↗

Aspirin versus coumadin in the prevention of reocclusion and recurrent ischemia after successful thrombolysis: a prospective placebo-controlled angiographic study. Results of the APRICOT Study.

BACKGROUND: Successful coronary thrombolysis involves a risk for reocclusion that cannot be prevented by invasive strategies. Therefore, we studied the effects of three antithrombotic regimens on the angiographic and clinical courses after successful thrombolysis. METHODS AND RESULTS: Patients treated with intravenous thrombolytic therapy followed by intravenous heparin were eligible when a patent infarct-related artery was demonstrated at angiography < 48 hours. Three hundred patients were randomized to either 325 mg aspirin daily or placebo with discontinuation of heparin or to Coumadin with continuation of heparin until oral anticoagulation was established (international normalized ratio, 2.8-4.0). After 3 months, in which conservative treatment was intended, vessel patency and ventricular function were reassessed in 248 patients. Reocclusion rates were not significantly different: 25% (23 of 93) with aspirin, 30% (24 of 81) with Coumadin, and 32% (24 of 74) with placebo. Reinfarction was seen in 3% of patients on aspirin, in 8% on Coumadin, and in 11% on placebo (aspirin versus placebo, p < 0.025; other comparison, p = NS). Revascularization rate was 6% with aspirin, 13% with Coumadin, and 16% with placebo (aspirin versus placebo, p < 0.05; other comparisons, p = NS). Mortality was 2% and did not differ between groups. An event-free clinical course was seen in 93% with aspirin, in 82% with Coumadin, and in 76% with placebo (aspirin versus placebo, p < 0.001; aspirin versus Coumadin, p < 0.05). An event-free course without reocclusion was observed in 73% with aspirin, in 63% with Coumadin, and in 59% with placebo (p = NS). An increase of left ventricular ejection fraction was only found in the aspirin group (4.6%, p < 0.001). CONCLUSIONS: At 3 months after successful thrombolysis, reocclusion occurred in about 30% of patients, regardless of the use of antithrombotics. Compared with placebo, aspirin significantly reduces reinfarction rate and revascularization rate, improves event-free survival, and better preserves left ventricular function. The efficacy of Coumadin on these end points appears less than that of aspirin. The still-high reocclusion rate emphasizes the need for better antithrombotic therapy in these patients.

Aged↗

Characterization of hypertensive subjects who become normotensive during three months of office BP follow-up: comparison with subjects with sustained hypertension and normotensives, and follow-up after two years.

After an observation period of three months, 83% of new hypertensives (n = 84), identified in a population survey, became normotensive. Those with sustained hypertension (n = 14) were compared with 14 initially hypertensives who became normotensive and 14 normotensives, matched for age and sex, using ambulatory and exercise BP and echocardiography (both M-mode and Doppler). The initially hypertensive group (n = 11) was re-examined after two years follow-up. The 24h mean ambulatory and submaximal systolic exercise BP did not differ between sustained (139/92 and 210 mmHg) and initially hypertensives (143/95 and 217 mmHg), being significantly lower in the normotensive group (129/85 and 198 mmHg). Left ventricular mass did not differ between the initially hypertensive and the normotensive groups, being significantly higher in the sustained hypertensives. In both hypertensive groups, as compared with normotensives, the ratio between flow velocity in early and late diastole (E/A ratio) tended to be lower and the early diastolic deceleration time (DT) was significantly shorter. After two years, in the untreated initially hypertensives, office DBP had increased to hypertensive values, without change in ambulatory BP, left ventricular mass or early diastolic deceleration time. The E/A ratio had decreased to a level < 1. We conclude that the subjects who became normotensive after three months office BP follow-up have a BP load and signs of compromised left ventricular diastolic function similar to that of the sustained hypertensives, but without increased left ventricular mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Uptake of radioligands by rat heart and lung in vivo: CGP 12177 does and CGP 26505 does not reflect binding to beta-adrenoceptors.

The biodistribution of (-)-4-(3-t-butylamino-2-hydroxypropoxy)-[5,7-3H-benzimidazol-2-one (CGP12177, a non-selective beta-adrenoceptor antagonist) and 1-[2-(3-carbamoyl-4-hydroxy)-(5-3H-phenoxy)]-2-propanol methanesulfonate, (CGP26505, a beta 1-adrenoceptor antagonist) was studied in rats pretreated with various alpha- and beta-adrenoceptor blocking drugs (5 min before 3H injection, in dosages at which the drugs demonstrated the expected selectivity). Cardiac and pulmonary radioactivity were measured after 10 min, when specific binding was maximal. Uptake of [3H]CGP12177 was linked to binding to beta-adrenoceptors since it was not affected by prazosin or yohimbine, and was equally well inhibited by propranolol, unlabelled CGP12177 and isoprenaline. Moreover, atenolol and CGP20712A inhibited [3H]CGP12177 uptake in heart (predominantly beta 1-adrenoceptors) more potently than ICI 118,551, while in lungs (predominantly beta 2-adrenoceptors) ICI 118,551 was more potent than atenolol or CGP20712A. In contrast, [3H]CGP26505 uptake in the target organs was equally effectively inhibited by propranolol and ICI 118,551, and significantly lowered by alpha-adrenoceptor antagonists. We conclude that [11C]CGP12177, but not [11C]CGP2605 will be suitable for positron emission tomography imaging of beta-adrenoceptors in animals.

Adrenergic alpha-Antagonists↗

Electropharmacologic effects and pharmacokinetics of almokalant, a new class III antiarrhythmic, in patients with healed or healing myocardial infarcts and complex ventricular arrhythmias.

The electropharmacologic effects and pharmacokinetics of almokalant, a new class III antiarrhythmic, were investigated in a randomized, placebo-controlled, double-blind study, and efficacy was evaluated. Ten post-myocardial infarction patients with complex ventricular arrhythmias were included and received, in randomized order on consecutive days, 4.5 mg (12.8 mumol) of almokalant or placebo intravenously over 10 minutes. One patient received infusion at a higher rate and developed self-terminating torsades de pointes. In the remaining 9 patients the corrected QT interval increased significantly: At the end of placebo infusion the corrected QT was 445 +/- 18 ms and after almokalant 548 +/- 53 ms (p = 0.0015). The signal-averaged electrocardiographic parameters did not change. The number of ventricular premature complexes decreased significantly during the first 15 minutes after almokalant infusion (p = 0.04). No additional proarrhythmic or other significant adverse events were noted. The almokalant plasma concentration showed a biphasic decrease with an elimination half-life of 2.4 +/- 0.1 hours. Almokalant was rapidly cleared from the body with a clearance of 11 +/- 1 ml/min/kg. When given with certain precautions almokalant appears safe and well-tolerated and may be antiarrhythmic by prolonging refractoriness.

Adult↗

Comparison between New York Heart Association classification and peak oxygen consumption in the assessment of functional status and prognosis in patients with mild to moderate chronic congestive heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy.

To compare the value of the New York Heart Association (NYHA) classification and measurement of peak oxygen consumption (VO2) in the assessment of functional status and prognosis in patients with mild to moderate chronic congestive heart failure (CHF), 94 patients with clinically stable NYHA class II and III CHF were prospectively studied. In all patients, left ventricular ejection fraction was less than or equal to 40% (mean 22 +/- 9); 49 patients were in NYHA class II, and 45 were in NYHA class III. Mean peak VO2 was 17 +/- 5 ml/min/kg. During a follow-up period of 23 +/- 11 months, 21 patients died. The 1-, 2- and 3-year cumulative survival rates for the 94 patients were 88, 79 and 69%, respectively. Functional status, as assessed both by peak VO2 and NYHA classification, and left ventricular ejection fraction were significantly worse in the group of nonsurvivors. The most powerful independent predictor of mortality was peak VO2. Although mean peak VO2 was significantly higher in NYHA class II than in NYHA class III (20 +/- 4 vs 13 +/- 3 ml/min/kg, p less than 0.0001), categorization into subgroups on the basis of the attained peak VO2 revealed a marked discrepancy with the NYHA classification. Nevertheless, the survival curves of patients subdivided at a peak VO2 of 16 ml/min/kg showed a strong resemblance with survival curves of both NYHA classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

Low-dose amiodarone for maintenance of sinus rhythm after cardioversion of atrial fibrillation or flutter.

OBJECTIVE: To study efficacy and safety of low-dose amiodarone for maintenance of sinus rhythm after electrical cardioversion of atrial fibrillation or flutter. DESIGN: Nonrandomized trial; mean duration of follow-up, 20.7 months. SETTING: Referral center; institutional practice; both hospitalized and ambulatory care. PATIENTS: Eighty-nine consecutive patients having chronic atrial fibrillation or flutter and eligible for cardioversion. Patients had failed previous treatment aimed at maintaining sinus rhythm. During follow-up one patient was withdrawn because of side effects; all patients were available for follow-up. INTERVENTION: Before cardioversion, patients received 600 mg of amiodarone daily during a 4-week loading period. After conversion, the daily maintenance dose was 204 +/- 66 mg (mean +/- SD). MAIN OUTCOME MEASURES: Arrhythmia recurrence and adverse effects causing drug discontinuation. RESULTS: During loading, 15 patients (16%) converted, and after electrical cardioconversion, 90% of all patients had sinus rhythm. Actuarially, 53% of these patients were still in sinus rhythm after 3 years. In patients with compromised left ventricular function, 93% maintained sinus rhythm after 6 months. One patient died due to congestive heart failure. Intolerable side effects occurred in one patient. No proarrhythmia was observed. Logistic regression analysis revealed that amiodarone was ineffective in patients with mitral stenosis or chronic arrhythmia. CONCLUSIONS: Low-dose amiodarone is effective for maintaining sinus rhythm in patients with difficult to treat chronic atrial fibrillation or flutter and is associated with a low incidence of serious side effects.

Amiodarone↗

Late potentials in a bradycardia-dependent long QT syndrome associated with sudden death during sleep.

The purpose of this study was to determine the incidence of late potentials and their relation to QT prolongation in a family with a high incidence of sudden death during sleep at a young age and bradycardia-dependent QT prolongation (n = 9) and to compare the findings with those in consanguineous family members without QT prolongation (n = 13). Six (67%) of the 9 family members with QT prolongation had late potentials on the signal-averaged electrocardiogram (ECG) compared with 1 of the 13 normal subjects (p less than 0.007). Positive predictive accuracy of the signal-averaged ECG for the detection of subjects with QT prolongation was 86%; negative predictive accuracy was 80%. During exercise testing, the QT interval normalized, whereas late potentials did not change significantly. Exercise testing did not reveal the presence of coronary artery disease as a possible cause of late potentials. It is concluded that 1) compared with family members with a normal QT interval, patients with this type of bradycardia-dependent QT prolongation have a high incidence of late potentials; 2) late potentials persist despite normalization of the QT interval at high heart rates, indicating that there is no direct relation between late potentials and QT prolongation; and 3) late potentials are not caused by coronary artery disease in these subjects. Therefore, the detection of late potentials might be a new aid in the detection and risk stratification of patients with the long QT syndrome. Late potentials possibly indicate a substrate for ventricular tachyarrhythmias in this type of bradycardia-dependent QT prolongation.

Adolescent↗

Triggered activity as arrhythmogenic mechanism after myocardial infarction: clinical and electrophysiologic study of one case.

In a woman with an old infarction and sustained ventricular tachycardia, tachycardias were only inducible after short-long RR sequences. After isoprenaline, tachycardias became incessant and all were preceded by short-long RR sequences. This strongly suggests that triggered activity plays a role in initiation of ventricular tachycardias in postinfarction patients.

Aged↗