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Biomedical subjects

Peter S Hansen

Publications and source records attributed to Peter S Hansen.

6 recordsLinked to original sources
PubMed2003

Chronic amiodarone-induced inhibition of the Na+-K+ pump in rabbit cardiac myocytes is thyroid-dependent: comparison with dronedarone.

OBJECTIVE: To examine the thyroid-dependence of the effect of amiodarone on the sarcolemmal Na(+)-K(+) pump, and the effect on the pump of dronedarone, a deiodinated amiodarone congener without influence on thyroid status. METHODS: New Zealand white rabbits underwent total thyroidectomy, sham thyroidectomy or thyroidectomy and concomitant oral amiodarone therapy. After 5 weeks, Na(+)-K(+) pump current was measured using the whole-cell patch-clamp technique in isolated ventricular myocytes. Pump current was also measured in myocytes isolated from a separate group of rabbits not subjected to thyroidectomy but treated with dronedarone, or placebo for 3 weeks. RESULTS: Treatment of thyroidectomised rabbits with amiodarone caused a significant prolongation of the corrected QT interval (QT(c)) and sinus cycle length. Na(+)-K(+) pump current measured in myocytes isolated from thyroidectomised rabbits was significantly lower than pump current in myocytes from sham-operated controls. However, treatment of thyroidectomised rabbits with amiodarone did not cause any additional decrease in pump current. Treatment with dronedarone caused prolongation of QT(c). However, it had no effect on Na(+)-K(+) pump current. CONCLUSIONS: The inhibitory effect of amiodarone on Na(+)-K(+) pump current is thyroid-dependent, whereas the effects on heart rate and QT(c) are at least partially mediated by thyroid-independent mechanisms. In contrast to its parent compound, dronedarone has no significant effects on the activity of the Na(+)-K(+) pump.

Amiodarone↗
PubMed2002

Sequential versus simultaneous biventricular resynchronization for severe heart failure: evaluation by tissue Doppler imaging.

BACKGROUND: Cardiac resynchronization therapy (CRT) by means of simultaneous biventricular pacing improves left ventricular systolic performance and synchrony in patients with heart failure and bundle-branch block. We used tissue tracking and 3D echocardiography to evaluate the impact of sequential CRT with individualized interventricular delay programming. METHODS AND RESULTS: Twenty consecutive patients with severe heart failure and left bundle-branch block were included. Tissue tracking and 3D echocardiography were carried out before and on the day after pacemaker implantation. Eleven different interventricular delays were examined in each patient. Patients were reexamined after 3 months. Simultaneous CRT immediately reduced the extent of myocardium displaying delayed longitudinal contraction (DLC) from 48.6+/-16% to 23.2+/-13% (P<0.01) and increased left ventricular ejection fraction percentage (LVEF%) from 22.4+/-6% to 29.7+/-5% (P<0.01). However, optimum sequential CRT caused a further reduction in the extent of DLC from 23.2+/-13% to 11.1+/-7.2% (P<0.01), with a simultaneous increase in LVEF% (from 29.7+/-5% to 33.9+/-6%, P<0.01). Three months of optimum sequential CRT further improved LVEF% (from 33.6+/-6% to 38.6+/-7.2%, P<0.01). Tissue tracking detected the segments with DLC, and their location determined optimum interventricular delay programming. Compared with simultaneous CRT, sequential CRT increased diastolic filling time by 7+/-2.5%. CONCLUSIONS: Compared with simultaneous CRT, sequential CRT significantly improves left ventricular systolic and diastolic performance. Tissue tracking can be used to select optimum interventricular delay during CRT.

Aged↗
PubMed2002

Prevalence of coronary occlusion and outcome of an immediate invasive strategy in suspected acute myocardial infarction with and without ST-segment elevation.

The prevalence of flow-limiting coronary lesions at the time of presentation in patients with non-ST-segment elevation myocardial infarction (NSTEMI) is unknown. Because rational reperfusion strategies depend on early, accurate identification of coronary flow limitation, we performed coronary angiography at the time of presentation of patients with suspected NSTEMI. We also evaluated outcomes of an immediate interventional strategy. A comparison is made with suspected ST-segment elevation myocardial infarction (STEMI). Unselected consecutive patients with suspected STEMI or NSTEMI were enrolled in a prospective observational cohort study. Suspected STEMI was defined according to standard criteria. Suspected NSTEMI was identified by clinical evaluation of symptoms, electrocardiographic changes, persistence of ischemic pain for >20 minutes despite treatment, and/or hemodynamic instability. Biochemical evidence of myocardial necrosis on presentation was not mandatory. An immediate, around-the-clock invasive strategy was applied. Significant coronary lesions were found in 94% of 279 patients with suspected STEMI and in 90% of 125 patients with suspected NSTEMI, and coronary occlusion or flow limitation was present in 75% and 63% of patients, respectively. Immediate percutaneous coronary intervention was performed in 74% and 60%, respectively, and an additional 13% and 18%, respectively, had coronary artery bypass surgery during the index admission. In-hospital mortalities in the patients with suspected STEMI and NSTEMI were 4.7% and 5.6%, respectively. An additional 1.9% and 2.5% died at 6 months. The prevalence of coronary flow limitation in clinically suspected NSTEMI is almost as high as in suspected STEMI. Short- and long-term outcomes of an immediate invasive strategy are similar for the 2 conditions.

Adult↗
PubMed2002

Exaggeration of nonculprit stenosis severity during acute myocardial infarction: implications for immediate multivessel revascularization.

OBJECTIVES: This study was designed to assess the prevalence and clinical significance of exaggerated nonculprit lesion stenosis in the setting of acute (<12 h) myocardial infarction (AMI). BACKGROUND: Although microvascular spasm may reduce nonculprit artery flow during AMI, it is unknown whether increased tone may exaggerate nonculprit lesion severity. METHODS: In patients with additional angiography within nine months of AMI, and significant nonculprit lesions imaged in matching views, stenosis severity was compared between studies in a random blinded fashion using validated quantitative coronary angiography software. Baseline demographics, medications, hemodynamics at each study, and clinical status at follow-up (infarct/unstable angina/stable angina) were used to determine the independent influence of the infarct presentation on stenosis exaggeration. RESULTS: From 548 patients with AMI (1/99 to 6/01, 321 with multivessel disease), 112 had additional angiography; of these 48 had 59 lesions suitable for analysis. Between infarct and noninfarct angiograms there was a significant change in minimal lumen diameter (1.53 +/- 0.51 mm vs. 1.78 +/- 0.65 mm, p < 0.001) and percentage stenosis (49.3 +/- 14.5% vs. 40.4 +/- 16.6%, p < 0.0001) of the nonculprit lesion without significant change in reference segment diameter, which was not predicted by changes in medication or hemodynamics. Twenty-one percent of patients had lesions >50% at AMI that were <50% at non-AMI angiography. Infarct versus noninfarct setting was the only significant independent predictor of change in nonculprit stenosis. CONCLUSIONS: Significant exaggeration of nonculprit lesion stenosis severity occurs at infarct angiography, which may affect revascularization decision making in an appreciable number of patients.

Aged↗
PubMed2002

Dependence of Na+-K+ pump current-voltage relationship on intracellular Na+, K+, and Cs+ in rabbit cardiac myocytes.

To examine effects of cytosolic Na+, K+, and Cs+ on the voltage dependence of the Na+-K+ pump, we measured Na+-K+ pump current (Ip) of ventricular myocytes voltage-clamped at potentials (Vm) from 100 to +60 mV. Superfusates were designed to eliminate voltage dependence at extracellular pump sites. The cytosolic compartment of myocytes was perfused with patch pipette solutions with a Na+ concentration ([Na]pip) of 80 mM and a K+ concentration from 0 to 80 mM or with solutions containing Na+ in concentrations from 0.1 to 100 mM and K+ in a concentration of either 0 or 80 mM. When [Na]pip was 80 mM, K+ in pipette solutions had a voltage-dependent inhibitory effect on Ip and induced a negative slope of the Ip-Vm relationship. Cs+ in pipette solutions had an effect on Ip qualitatively similar to that of K+. Increases in Ip with increases in [Na]pip were voltage dependent. The dielectric coefficient derived from [Na]pip-Ip relationships at the different test potentials was 0.15 when pipette solutions included 80 mM K+ and 0.06 when pipette solutions were K+ free.

Animals↗