Search PubMed⌕ Search

Biomedical subjects

P Hanrath

Publications and source records attributed to P Hanrath.

At least 163 records · Page 9Linked to original sources
PubMed1997

A prospective, randomized comparison of temperature-controlled vs manually delivered radiofrequency catheter ablation in patients undergoing atrioventricular nodal modification or accessory pathway ablation.

AIMS: In a prospective, randomized study, the effect of temperature control on radiofrequency catheter ablation was compared in 69 patients undergoing atrioventricular nodal modification (n = 32) or ablation of an accessory pathway (n = 37). METHODS AND RESULTS: Thirty-five patients were randomized to temperature control, 34 to manually delivered radiofrequency ablation. The success rate was 92.5% for accessory pathway ablation and 100% for atrioventricular nodal modification. Mapping duration was significantly reduced only in patients undergoing atrioventricular nodal modification. The number of applications was higher for manually delivered ablation in patients undergoing atrioventricular nodal modification (5.6 +/- 1.1 vs 1.9 +/- 0.4, P = 0.004) as was the cumulative energy delivered (5034 +/- 1008 vs 2054 +/- 517 W, P = 0.013) whereas the mean power per application was higher with temperature control (41.4 +/- 1.8 vs 34.1 +/- 1.1 W, P = 0.002). No significant differences in these parameters were found in patients undergoing accessory pathway ablation. Coagulum formation on the catheter tip was observed more often with manually delivered ablation 5.3% vs 0.9%, P = 0.026). The success rate with the initially randomized application mode was higher for temperature control (94.3 vs 61.8%, P = 0.003). CONCLUSIONS: Temperature control during radiofrequency current ablation significantly reduces mapping duration, necessary applications and cumulative energy in atrioventricular nodal modification, but not accessory pathway ablation. Coagulum formation on the catheter tip still occurs but is significantly reduced compared to manually delivered radiofrequency current.

Atrioventricular Node↗
PubMed1997

Functional characteristics of myocardial bridging. A combined angiographic and intracoronary Doppler flow study.

AIMS: Combined quantitative coronary angiography and intracoronary Doppler flow velocity measurements were performed to study the underlying haemodynamic mechanisms leading to myocardial ischaemia in patients with myocardial bridging in the absence of coronary artery disease. METHODS AND RESULTS: In 42 symptomatic patients with myocardial bridging of the left anterior descending coronary artery, quantitative coronary angiography was used to measure absolute and relative vessel diameters during systole and diastole. In 14 patients, serial frame-by-frame diameter quantification during a complete cardiac cycle was performed. Intracoronary blood flow velocities were determined using a 0.014 inch Doppler flow guide wire proximal, within, and distal to myocardial bridges, and coronary flow reserve was calculated. Quantitative coronary angiography revealed a maximal systolic lumen diameter reduction of 71 +/- 16% with a persistent diameter reduction of 35 +/- 13% during mid-diastole. Flow velocities revealed increased average diastolic peak flow velocities within myocardial bridges of 38.6 +/- 19 cm.s-1 vs 22.4 +/- 7.7 cm.s-1 proximal and 18.6 +/- 4.6 cm.s-1 distal (P < 0.001), which increased during rapid pacing (64.7 +/- 25 cm.s-1, P < 0.001 vs baseline). Coronary flow reserve distal to myocardial bridges was 2.3 +/- 0.9 (vs 2.9 +/- 0.9 proximal, P < 0.05). There was a characteristic Doppler flow profile within myocardial bridges with an early diastolic overshoot, which was further augmented during rapid pacing. CONCLUSION: Myocardial bridging is characterized by a delay in diastolic lumen gain and a concomitant increase in diastolic intracoronary Doppler flow velocities, which are enhanced by rapid pacing. In combination with a reduced coronary flow reserve and anginal symptoms these findings support the concept of a haemodynamically significant obstruction to coronary flow due to myocardial bridging in a selected subset of patients.

Blood Flow Velocity↗
PubMed1997

Polarity reversal improves defibrillation efficacy in patients undergoing transvenous cardioverter defibrillator implantation with biphasic shocks.

The purpose of this study was to determine the influence of polarity reversal on DFT in patients undergoing implantation of nonthoracotomy defibrillators with biphasic shocks. Previous studies have shown higher defibrillation efficacy with using the distal electrode as anode implantation of nonthoracotomy defibrillators and monophasic shocks. However, it is as yet unclear whether biphasic shock defibrillation will also be influenced by polarity reversal. Using a transvenous lead system with a proximal electrode in the superior caval vein and a distal electrode in the RV apex, 27 patients undergoing defibrillator implantation were randomized to DFT testing "initial" (distal electrode = cathode) or "reversed" polarity (distal electrode = anode). Defibrillation energy was reduced stepwise until defibrillation failure occurred. At this point, polarity was switched and testing continued until the lowest energy requirement was determined for both polarities. With reversed polarity, DFT was 11.1 +/- 5.7 J versus 13.3 +/- 5.8 J with polarity (P = 0.033). This means a 17% reduction of the DFT. In 10 patients, the threshold was lower with reversed, whereas in 3 patients it was lower with initial polarity. In conclusion, changing electrode polarity in transvenous implantable defibrillators with biphasic shocks may significantly influence defibrillation energy requirements. Therefore, polarity reversal should always be attempted before considering patch implantation.

Adult↗
PubMed1997

Transcoronary venous radiofrequency catheter ablation of ventricular tachycardia.

Ventricular tachycardias in coronary artery disease arise mostly from endocardial sites. However, little is known about the site of origin in other diseases. We present the case of an incessant, adenosine-sensitive ventricular tachycardia arising from the lateral wall of the left ventricle in a patient with mildly reduced left ventricular function. Intracardiac mapping suggested an epicardial origin, and the tachycardia was successfully ablated from a coronary sinus branch. After ablation, left ventricular function returned to normal. Transcoronary venous radiofrequency catheter ablation is a new approach for the treatment of ventricular tachycardia. Its value in the management of other types of ventricular tachycardia has yet to be determined.

Adult↗
PubMed1997

Congenital quadricuspid aortic valve anomaly associated with hypertrophic non-obstructive cardiomyopathy: a case report and review of the literature.

A case is reported of a 38 year old woman without known cardiac congenital abnormality but a history of well controlled arterial hypertension who was admitted to hospital after successful resuscitation at home following cardiac arrest. There was no evidence of myocardial infarction on 12-lead electrocardiogram but there were signs of left ventricular hypertrophy. Transoesophageal echocardiography revealed a rare quadricuspid aortic valve (QAV) malformation with concomitant mild aortic regurgitation. The left ventricle showed a massive concentric hypertrophy without obstruction. The patient was eventually transferred in a persistent vegetative state to a home care facility. A review of the literature revealed 70 cases of QAV diagnosed by transthoracic or transoesophageal echocardiography (26 cases), at necropsy (25), during surgery (15), and during angiography (4). The present case is the first report of QAV associated with non-obstructive hypertrophic cardiomyopathy.

Adult↗
PubMed1997

Effect of myocardial viability assessed by technetium-99m-sestamibi SPECT and fluorine-18-FDG PET on clinical outcome in coronary artery disease.

UNLABELLED: PET imaging of myocardial perfusion and metabolism identifies regional viability as well as patients at high risk for future cardiac events. This study evaluated a combined "hybrid" imaging approach using 99mTc-sestamibi SPECT and [18F]fluoro-2-deoxy-D-glucose (FDG) PET with regard to reversibility of regional dysfunction and to patient clinical outcome during a 2-yr follow-up. METHODS: In this study, 161 consecutive patients underwent baseline viability imaging. All had regional wall motion (RWM) abnormalities and 88% had a history of previous myocardial infarction. Regions were classified by semiquantitative analysis of sestamibi and FDG uptake as normal, mild match, mismatch or scar. For clinical outcome, patients were divided into three groups: predominantly scar tissue (Group A, n = 90), mild match (Group B, n = 26) and mismatch (Group C, n = 45). Treatment was performed with the knowledge of nuclear results. Cardiac events during follow-up were defined as death, myocardial infarction, unstable angina requiring revascularization, heart transplantation and survived resuscitation. RESULTS: Patients were followed for 29 +/- 6 mo. Revascularization rate was 30% in Group A, 81% in Group B and 80% in Group C, whereas the other patients were treated by medication. Only Group C demonstrated a significant reduction of cardiac events after revascularization, whereas, particularly in Group A, revascularization did not influence the frequency of events. Subjective assessment of angina pectoris and heart failure revealed more patients with improvement after revascularization as compared with conservative treatment. Of the 84 revascularized patients, 61 underwent follow-up angiography at 5 +/- 2 mo with RWM analysis using the centerline method. RWM improved only in mismatch regions from -2.2 +/- 1.0 s.d. to -1.0 +/- 1.4 s.d. (p < 0.01), whereas regions with a mild match or scar did not change. CONCLUSION: Nuclear imaging using 99mTc-sestamibi SPECT and [18F]FDG PET allows diagnosis of viability in regions with reduced perfusion and function with prognostic implications for functional outcome as well as for identification of patients who benefit most from revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1997

Approach to computer-based medication planning and coordination support in intensive care units.

Due to more and more complex diagnosis and therapy measures, the critical care of patients requires an extensive work organisation which comprises patient, doctors, nurses and external services (e.g., central laboratory). In this organisation, the documentation plays a major role for the planning and coordination of work procedures and information flow within the medical staff. Various studies in intensive care units (ICU) reveal that the complex work organisation and the related information flow are faulty. Breakdowns are often caused by a lack of coordination between doctors and nurses and by poor transparency of work procedures. A typical example is the incorrect application of a doctor's medication orders by a nurse because she might have overseen a plan modification. This intransparency increases the strain on the medical staff and might result in critical effects on the patient. One approach to design a computer support for medication planning as well as the coordination when executing medication plans is given by work flow models. This paper shows that work flow models could be used to improve deficiencies in medication planning and coordination. Furthermore, it is demonstrated how such a support can be mediated to the user through an appropriately designed user interface.

Communication↗
PubMed1996

Fate of the resting perfusion defect as assessed with technetium-99m methoxy-isobutyl-isonitrile single-photon emission computed tomography after successful revascularization in patients with healed myocardial infarction.

It is concluded that in patients with healed myocardial infarction, MIBI uptake at rest underestimates myocardial viability and may improve significantly if blood flow is restored. Patients with MIBI defects at rest may therefore take advantage of revascularization.

Coronary Circulation↗
PubMed1996

Effects of metoprolol on myocardial beta-adrenoceptors and Gi alpha-proteins in patients with congestive heart failure.

OBJECTIVE: In human heart failure downregulation of beta-adrenoceptors and upregulation of Gi-protein alpha-subunits (Gi alpha) results desensitization of the myocardial beta-adrenergic signal transduction pathway and reduced positive inotropic effects of catecholamines. Metoprolol treatment has been shown to restore the reduced beta-adrenoceptor density in dilated cardiomyopathy. The main objective of the present study was to investigate whether metoprolol also decreases the elevated inhibitory Gi alpha levels in patients suffering from congestive heart failure. METHODS: Total Gi alpha was determined by pertussis toxin-catalysed ADP ribosylation and beta 1- and beta 2-adrenoceptor densities by radioligand binding in right ventricular myocardial biopsies of 18 patients with dilated or ischaemic cardiomyopathy (NYHA II-IV) before and after 3 months of therapy. Nine controls were treated with conventional therapy only [diuretics, digitalis, nitrates, angiotensin-converting enzyme (ACE) inhibitors], and nine received the beta 1-selective blocker metoprolol in addition (mean 98 +/- 12 mg daily). RESULTS: In biopsies from patients treated with metoprolol, Gi alpha significantly decreased to 74% of predrug value and total beta-adrenoceptor increased by a selective increase in beta 1-adrenoceptors (44.7 vs 34.0 fmol mg-1 protein). These effects were accompanied by significantly increased oxygen uptake at the anaerobic threshold (8.65 vs 6.95 ml . kg-1 . min-1). In the control group no significant changes in biochemical and clinical parameters occurred. CONCLUSION: Metoprolol partly reverses Gi alpha-upregulation and beta-adrenoceptor downregulation in heart failure, which might contribute to the clinical improvement of patients treated with beta-blockers.

Adrenergic beta-Antagonists↗
PubMed1996

Analysis of interinstitutional observer agreement in interpretation of dobutamine stress echocardiograms.

OBJECTIVES: This study sought to determine the degree of interinstitutional agreement in the interpretation of dobutamine stress echocardiograms. BACKGROUND: Dobutamine stress echocardiography involves subjective interpretation. Consistent methods for acquisition and interpretation are of critical importance for obtaining high interobserver agreement and for facilitating communication of test results. METHODS: Five experienced centers were each asked to submit 30 dobutamine stress echocardiograms (dobutamine up to 40 micrograms/kg body weight per min and atropine up to 1 mg) obtained in patients undergoing coronary angiography. Thus, a total of 150 dobutamine stress echocardiograms were interpreted by each center without knowledge of any other patient data. Left ventricular wall motion was assessed using a 16-segment model but was otherwise not standardized. No patient was excluded because of poor image quality or inadequate stress level. Echocardiographic image quality was assessed using a five-point scale. RESULTS: Angiographically significant coronary artery disease (> or = 50% diameter stenosis) was present in 95 patients (63%). By a majority decision (three or more centers), the sensitivity, specificity and accuracy of dobutamine echocardiography were 76%, 87% and 80%, respectively. Abnormal or normal results of stress echocardiography were agreed on by four or all five of the centers in 73% of patients (mean kappa value 0.37, fair agreement only). Agreement on the left anterior descending artery territory (78%) was similar to that for the combined right coronary artery/left circumflex artery territory (74%), and for specific segments the agreement ranged from 84% to 97% and was highest for the basal anterior segment and lowest for the basal inferior segment. Agreement was higher in patients with no (82%) or three-vessel coronary artery disease (100%) and lower in patients with one- or two-vessel disease (61% and 68%, respectively). Agreement on positivity or negativity of stress test results was 100% for patients with the highest image quality but only 43% for those with the lowest image quality (p = 0.003). CONCLUSIONS: The current heterogeneity in data acquisition and assessment criteria among different centers results in low interinstitutional agreement in interpretation of stress echocardiograms. Agreement is higher in patients with no or advanced coronary artery disease and substantially lower in those with limited echocardiographic image quality. To increase interinstitutional agreement, better standardization of image acquisition and reading criteria of stress echocardiography is recommended.

Cardiotonic Agents↗
PubMed1996

Myocyte degeneration and cell death in hibernating human myocardium.

OBJECTIVES: The aim of this study was to analyze the morphologic characteristics of myocyte degeneration leading to replacement fibrosis in hibernating myocardium by use of electron microscopy and immunohistochemical techniques. BACKGROUND: Data on the ultrastructure and the cytoskeleton of cardiomyocytes in myocardial hibernation are scarce. Incomplete or delayed functional recovery might be due to variable degree of cardiomyocyte degeneration in hibernating myocardium. METHODS: In 24 patients, regional wall motion abnormalities were analyzed by use of the centerline method before and 6 +/- 1 months after coronary artery bypass surgery. Preoperative technetium-99m sestamibi uptake was measured by single-photon emission computed tomography for assessing regional perfusion. Fluorine-18 fluorodeoxyglucose uptake was measured by positron emission tomography to assess glucose metabolism. Transmural biopsy specimens were taken during coronary artery bypass surgery from the center of the hypocontractile area of the anterior wall. RESULTS: The myocytes showed varying signs of mild-to-severe degenerative changes and an increased degree of fibrosis. Immunohistochemical analysis demonstrated disruption of the cytoskeletal proteins titin and alpha-actinin. Electron microscopy of the cell organelles and immunohistochemical analysis of the cytoskeleton showed a similarity in the degree of degenerative alterations. Group 1 (n = 11) represented patients with only minor structural alterations, whereas group 2 (n = 13) showed severe morphologic degenerative changes. Wall motion abnormalities showed postoperative improvements, and nuclear imaging revealed a perfusion-metabolism mismatch without significant differences between the groups. CONCLUSIONS: Long-term hypoperfusion causes different degrees of morphologic alterations leading to degeneration. Preoperative analysis of regional contractility and perfusion-metabolism imaging does not distinguish the severity of morphologic alterations nor the functional outcome after revascularization. The insufficient act of self-preservation in hibernating myocardium may lead to a progressive structural degeneration with an incomplete and delayed recovery of function after restoration of blood flow.

Adult↗
PubMed1996

Functional, angiographic and intracoronary Doppler flow characteristics in symptomatic patients with myocardial bridging: effect of short-term intravenous beta-blocker medication.

OBJECTIVES: We sought to define the effects of short-term beta-adrenergic blocking medication on intracoronary flow characteristics, clinical symptoms and angiographic diameter changes in patients with severe myocardial bridging of the left anterior descending coronary artery. BACKGROUND: Controversy exists regarding the pathophysiology, clinical relevance and optimal therapy in symptomatic patients with myocardial bridges because antianginal drugs have not been systematically tested. METHODS: In 15 symptomatic patients with myocardial bridging of the left anterior descending coronary artery, maximal lumen diameter reductions were evaluated by quantitative coronary angiography. There were no angiographic signs of coronary artery disease. Coronary blood flow velocities (using a 0.014-in. [0.035 cm] Doppler guide wire) were measured at rest, during atrial pacing and during intravenous administration of a short-acting beta-blocker (esmolol, 50 to 500 micrograms/kg body weight per min) with continuous atrial pacing. RESULTS: The maximal angiographic systolic lumen diameter reduction within the myocardial bridges was 83 +/- 9% at rest, with a persistent diastolic diameter reduction of 41 +/- 11% (mean +/- SD). Short-term intravenous beta-blocker therapy decreased the diameter reduction during both systole (from 83 +/- 9% to 62 +/- 11%) and diastole (from 41 +/- 11% to 30 +/- 9%, both p < 0.001). The average diastolic peak flow velocity was higher within the myocardial bridges (33 +/- 13 cm/s) than the proximal (26 +/- 13 cm/s) and distal bridges (17 +/- 4 cm/s, both p < 0.001). During tachypacing, average diastolic peak flow velocity increased within the bridged segments to 63 +/- 21 cm/s versus 29 +/- 12 cm/s in the proximal and 20 +/- 4 cm/s in the distal bridges (both p < 0.001). Beta-receptor blockade produced a return to baseline values (average diastolic peak flow velocity within bridge 35 +/- 16 cm/s, p < 0.001). ST segment changes and symptoms were abolished with beta-blocker administration. CONCLUSIONS: In patients with myocardial bridges, administration of short-acting beta-blockers during atrial pacing alleviates anginal symptoms and signs of ischemia. This effect was mediated by a reduction of vascular compression and maximal flow velocities within the bridged coronary artery segment.

Adrenergic beta-Antagonists↗
PubMed1996

Recovery of regional left ventricular dysfunction after coronary revascularization. Impact of myocardial viability assessed by nuclear imaging and vessel patency at follow-up angiography.

OBJECTIVES: This study sought to evaluate an imaging approach using technetium-99m sestamibi scintigraphy and positron emission tomography with fluorine-18 fluorodeoxyglucose for assessment of myocardial viability proved by serial quantitative left ventricular angiography. Furthermore, the influence of successful long-term revascularization on functional recovery was studied. BACKGROUND: Previous studies using positron emission tomography of myocardial perfusion and metabolism have demonstrated accurate identification of myocardial viability. However, most of these studies used a qualitative or semiquantitative wall motion analysis approach. METHODS: Nuclear imaging with semiquantitative analysis of tracer uptake was performed in 193 patients with regional wall motion abnormalities. Regions were categorized as normal, viable with perfusion/metabolism mismatch, viable without mismatch (intermediate) and scar. Seventy-two of 103 patients with subsequent revascularization underwent follow-up angiography. In 52 of 72 patients, changes in regional wall motion were measured by the centerline method from serial angiography. RESULTS: Wall motion improved in mismatch regions from -2.2 +/- 1.0 to -1.1 +/- 1.4 SD (p < 0.001). In contrast, regions with an intermediate pattern and those with scar did not improve. Restenosis or graft occlusion influenced functional outcome because regions with preoperative mismatch and successful long-term revascularization improved at follow-up (from -2.3 +/- 1.0 to -0.8 +/- 1.4 SD, p < 0.001), whereas wall motion did not change with recurrent hypoperfusion. Metabolic imaging added diagnostic information, particularly in regions with mild and moderate perfusion defects. CONCLUSIONS: This imaging approach allows detection of viability in regions with myocardial dysfunction. Wall motion benefits most in myocardium with perfusion/metabolism mismatch and successful long-term revascularization.

Aged↗