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Biomedical subjects

F W Amann

Publications and source records attributed to F W Amann.

At least 37 records · Page 2Linked to original sources
PubMed1999

Acute hemodynamic effects of alternate and combined site pacing in patients after cardiac surgery.

We hypothesized that pacing at sites other than the right ventricular (RV) apex or at two or more ventricular sites would activate the myocardium more rapidly and improve cardiac function in patients undergoing coronary revascularization or aortic valve replacement. Epicardial electrodes were placed on the right atrium (A), RV paraseptal area close to the RV apex (B), RV outflow tract (C), LV apex (D), in patients undergoing bypass surgery. At constant rate and AV delay, we measured CO during A pacing, DVI pacing at B, C, D, and various combinations of sites in random order in ten patients with EF > 50% and 27 patients with EF < or = 50%. When pacing at two sites, we made one electrode a cathode and one an anode and noted two distinct thresholds by careful observation of the 12-lead ECG. There were no significant differences in CO, systemic vascular resistance, systolic, or mean arterial pressure. Significant differences were noted in QRS duration, which increased progressively going from AAI to 3-site, 2-site, and single site pacing (P < 0.05 each comparison). Thus: (1) QRS duration correlated inversely with the number of ventricular sites paced; (2) despite this, CO did not improve irrespective of baseline EF; (3) multisite pacing produced multiple distinct thresholds which appeared to be related to the number of sites paced, and (4) unique ECG patterns confirmed multisite pacing.

Aortic Valve↗
PubMed1998

[Influence of various antithrombotic therapy methods on the incidence of subacute coronary stent occlusions, hemorrhagic complications and length of hospitalization].

BACKGROUND: The clinical benefit of coronary stenting is reduced by the risk of thrombotic stent occlusion as well as hemorrhagic complications of intensive antithrombotic therapy. We compared the influence of different antithrombotic therapies on the incidence of post-interventional complications and in-hospital stay duration. METHODS: After successful placement of a coronary stent, 334 consecutive patients were given different antithrombotic treatments in addition to aspirin 100 mg/d indefinitely: (1) phenprocoumon for 3 months (n = 47), (2) low molecular weight heparin 2 x 100 U/kg/d s.c. for 4 weeks (n = 90), (3) ticlopidine 2 x 250 mg/d and low molecular weight heparin 2 x 100 U/kg/d s.c. for 4 weeks (n = 72) and (4) ticlopidine 2 x 250 mg/d for 4 weeks (n = 125). RESULTS: Major events were subacute stent thrombosis in 17 patients (5%), and severe hemorrhagic complication in 20 patients (5.9%). The incidence of subacute stent thrombosis in groups 1 to 4 was 10.6%, 11%, 1.4% and 0.8% respectively. The use of ticlopidine was associated with a significant lowering of stent occlusions in univariate and multivariate analysis (p = 0.0013). Additional uni- and multivariate predictors were stent placement as a "bail-out" procedure (p = 0.033) and in patients with acute coronary syndrome (p = 0.049). Anticoagulant therapy was associated with a higher incidence of severe hemorrhagic complications (p < 0.01) and a prolonged in-hospital stay (p = 0.01). CONCLUSIONS: These results confirm that anti-thrombotic therapy with aspirin and ticlopidine combines low rates of subacute stent occlusion and hemorrhagic complications. Treatment with phenprocoumon and low molecular weight heparin does not improve the rate of subacute stent occlusion but increases hemorrhagic complications. Very low rates of stent occlusion permit short in-hospital stays with concomitant reduction in cost.

Acute Disease↗
PubMed1998

Systolic and diastolic function with alternate and combined site pacing in the right ventricle.

UNLABELLED: We hypothesized that pacing at two ventricular sites simultaneously would activate the myocardium more rapidly and improve ventricular function. We studied the effect of pacing at the right ventricular outflow tract (RVOT) and the RV apex (RVA) on systolic and diastolic function. In 14 patients with a reduced systolic ejection fraction < 40% (mean EF 32% +/- 4%) we measured RV pressures, left ventricular pressures, EF, cardiac output, peak dP/dt, peak negative dP/dt, and the time constant of relaxation, Tau, during intrinsic rhythm, atrial pacing and DVI pacing at the RVA, the RVOT, and both RV sites combined in random order. Repeated measures analysis of variance showed no significant differences in any of these parameters. The highest absolute values of dP/dt were observed during sinus rhythm and the lowest with RVA pacing. This parameter tended to improve progressively with pacing in the RVOT and at both sites. Peak negative dP/dt showed a similar nonsignificant trend. CONCLUSION: These data suggest that in patients with poor LV function, there may be subtle improvements in diastolic and systolic function with pacing in the RVOT and at combined sites in the RV compared to traditional RVA pacing.

Analysis of Variance↗
PubMed1997

[Limits of revascularization: interventional treatment possibilities in occlusion and restenosis after bypass operation].

Coronary artery bypass graft (CABG) surgery may be limited by incomplete revascularization, graft failure and progression of narrowing in the native coronary arteries. Ischemia in the first year after CABG, associated with anastomotic problems, can be safely and effectively treated with angioplasty. The rate of saphenous vein graft failure increases rapidly 8 years after CABG. Interventional strategy depends largely on lesion morphology. Focal stenoses can be treated with stents, with primary success rates > 90% and complication rates < 5%. Diffusely degenerated vein grafts and chronic total occlusions remain problematic for all catheter-based interventions. No randomized trial exists comparing reoperative CABG with angioplasty. In non-randomized data, neither therapy was clearly superior to the other. The underlying extent of disease primarily determines long-term survival. This suggests that control of risk factors may well be beneficial. In patients with recurrent symptoms unresponsive to medical therapy, referral for revascularization is reasonable. The choice of additional treatment may be made on the basis of clinical criteria and angiographic suitability, as well as patient preference.

Coronary Artery Bypass↗
PubMed1997

[After-care of the patient with myocardial infarct].

Patients after myocardial infarction are at a substantial risk for recurrent cardiac events; therefore, an optimal patient care is of great importance. Early revascularisation is one important contributor to the prognosis after myocardial infarction. Antithrombotic agents, betablockers, and ACE-inhibitors also contribute significantly to the improved outcome after myocardial infarction. Reduction of risk factors, in particular cessation of smoking and lowering of lipids are of highest importance to improve the prognosis after myocardial infarction.

Adrenergic beta-Antagonists↗
PubMed1997

[Secondary prevention in patients before and after percutaneous transluminal coronary angioplasty: 5-year follow-up].

Several studies have demonstrated substantial risk reduction by risk factor modification in patients with established coronary artery disease. The number of studies investigating the implementation of risk factor intervention in clinical practice, however, is limited. We have, therefore, recorded drug use and cardiovascular risk factors in all 148 patients who had undergone percutaneous coronary angioplasty (PTCA) in 1989 at the University Hospital, Zurich, on hospital admission, after 6 months and 5 years later. Most patients had antithrombotic treatment with little change over time (78%, 87% and 83% on admission, after 6 months and after 5 years respectively, p = 0.27). The use of beta-blockers decreased moderately after 5 years (73%, 81% and 61% respectively, p < 0.01). Calcium channel blockers were used frequently without significant change in the follow-up period (56%, 50% and 46%, p = 0.25). Five years after PTCA, 91% of patients with a history of hypertension were on antihypertensive drugs. The use of lipid-lowering drugs increased markedly (5%, 16% and 33% respectively, p < 0.01). However, only a small proportion of patients qualifying for lipid-lowering drugs according to Swiss guidelines were treated. The proportion of current smokers decreased from 26% on hospital admission in 1989 to 12% in 1994. We conclude that in our study population secondary prevention was generally satisfactorily implemented. However, better monitoring and treatment of increased lipid levels is mandatory.

Adrenergic beta-Antagonists↗
PubMed1997

Coronary vasomotion after percutaneous transluminal coronary angioplasty depends on the severity of the culprit lesion.

OBJECTIVES: This study sought to evaluate coronary vasomotor response to percutaneous transluminal coronary angioplasty (PTCA) and its influence on proximal and distal vessel diameters with regard to stenosis severity and coronary blood flow. BACKGROUND: Coronary vasoconstriction of the distal vessel segment has been reported after PTCA. This vasoconstrictive effect was thought to be due to balloon-induced injury of the vessel wall, with release of local vasoconstrictors or stimulation of the sympathetic system with release of catecholamines, or both. METHODS: Thirty-nine patients were prospectively studied before and after PTCA. Patients were classified into two groups according to the severity of the culprit lesion: group 1 = > or = 70% to < or = 85% diameter stenosis (n = 23); and group 2 = > 85% to < or = 95% diameter stenosis (n = 16). The coronary vessel diameter of the proximal and distal vessel segments as well as the minimal lumen diameter were determined by quantitative coronary angiography. In a subgroup of 16 patients, basal and maximal coronary flow velocity was measured before and after PTCA with the Doppler FloWire system. RESULTS: The groups were comparable with regard to age, gender, serum cholesterol levels and medical therapy. The proximal vessel segment remained unchanged after PTCA in group 1 ([mean +/- SD] 0.9 +/- 3.5%, p = 0.8) but showed vasodilation in group 2 (+13.7 +/- 3.6%, p < 0.05). However, the distal segment showed vasoconstriction in group 1 (-6.7 +/- 2.0%, p < 0.01) and vasodilation in group 2 (+31 +/- 8.0%, p < 0.01). A significant correlation was found between the change in distal vessel diameter after PTCA and stenosis severity (r = 0.61, p < 0.0001). Changes in blood flow were directly correlated to stenosis severity (r = 0.85, p < 0.002); that is, rest flow increased after PTCA in narrow lesions but remained unchanged in moderate lesions. The diameter changes in the distal vessel segment after PTCA were significantly related to flow changes (r = 0.90, p < 0.0001). Coronary distending pressure of the distal vessel segment increased significantly in both groups; however, this increase was significantly greater in group 2 than in group 1 (55 +/- 4 vs. 14 +/- 3 mm Hg, p < 0.0001). CONCLUSIONS: Coronary vasomotion of the proximal and distal vessel segments after PTCA depends on the severity of the culprit lesion; that is, vasoconstriction of the distal segment is found in patients with moderate lesions and vasodilation in those with severe lesions. Thus, vasomotion of the post-stenotic vessel segment depends on the severity of the culprit lesion and is influenced by changes in coronary flow or distending pressure, or both.

Angioplasty, Balloon, Coronary↗
PubMed1997

Vibration, acceleration, gravitation, and movement: activity controlled rate adaptive pacing during treadmill exercise testing and daily life activities.

Activity-based sensors for rate adaptive pacing have been available for several years and now include several different types: vibration; acceleration; gravitation; and movement. However, a systematic comparison evaluating the relative advantages and disadvantages of these various sensors has received little study. The purpose of the present study was to compare these sensor subtypes using treadmill testing and an outdoor test circuit, which simulated daily life activities and included both uphill and downhill walking. Pacemakers were strapped on the chest of healthy volunteers and connected to one channel of an ambulatory recording device, which also recorded the subject's intrinsic heart rate. The pacemakers were programmed using an initial treadmill test to standardize the rate responsive parameters for each device. Nine different pacemaker models were studied including 3 vibration-based (Elite, Synchrony, Metros), 4 acceleration-based (Relay, Excel, Ergos, Trilogy), 1 gravitational-based (Swing), and 1 movement-based (Sensorithm) device. All devices demonstrated a prompt rate response with casual walking on flat ground. The vibration-, gravitational-, and movement-based pacemakers showed a pronounced rate decline during more strenuous work, e.g., walking uphill. This phenomenon was absent in the accelerometer-based units. In particular, the vibration- and movement-based units showed a higher rate with walking downhill compared to uphill. An optimally tuned rate behavior on the treadmill usually did not provide an optimal rate behavior during daily activities and there was a tendency to overstimulation during low workload. The development of the two newest sensors (gravitational and movement) did not result in an improved performance of rate response behavior. Overall, the accelerometer-based pacemakers simulated or paralleled sinus rate behavior the most closely.

Acceleration↗
PubMed1997

Age and sex related changes in heart rate to ventilation coupling: implications for rate adaptive pacemaker algorithms.

Minute ventilation (VE) controlled rate adaptive pacemakers determine the paced rate increase during exercise by measuring changes in transthoracic impedance that have been shown to correlate well with VE. To determine the normal coupling of heart rate (HR) to VE this relationship was evaluated in 30 younger and 25 older, healthy subjects using peak cardiopulmonary exercise testing. After determining the anaerobic threshold (AT), the linear HR to VE slope was determined both below and above the AT. In addition, the entire curve of the HR to VE relationship was assessed by a "best fit" regression analysis method. The relationship of HR to VE was more often logarithmic in younger as compared to older subjects. The HR to VE slope below the AT was always steeper than above the AT in younger subjects. Females of both age subgroups demonstrated a significantly greater slope below and above the AT. For the appropriate programming of VE controlled, rate responsive pacemakers, one should take into consideration age- and sex-specific differences in the HR to VE relationship throughout exercise. Therefore, age- and sex-specific programmable features for rate responsive parameters should be incorporated into pacemakers using VE controlled rate adaptive algorithms.

Adult↗
PubMed1997

Deficiency of cholesteryl ester transfer protein. Description of the molecular defect and the dissociation of cholesteryl ester and triglyceride transport in plasma.

A patient is described who exhibited, despite excessively high postprandial triglyceride levels, high levels of HDL cholesterol. Measurement of CETP activity and mass in the patient's plasma showed values of less than 5% and 2%, respectively, of a normolipidemic plasma pool. The CETP cDNA of the patient exhibited a mutation (T-->G), turning codon 57 (TAT) of exon 2 into a stop codon (TAG) and abolishing a, XcmI restriction site. Digestion of directly amplified CETP cDNA from the patient with XcmI indicated the exclusive presence of CETP cDNA containing the mutation. Analysis of the corresponding region of the CETP gene indicated the patient to be heterozygous for the nonsense mutation at codon 57, a finding that can only be explained by the presence of a null allele in addition to the allele with the nonsense mutation. The combination of TG intolerance of uncertain cause, together with CETP deficiency due to a novel mutation, produced the paradoxical constellation--high levels of HDL cholesterol (172 mg/dL) associated with a high post-prandial lipemia of 1460 mg triglycerides/dL.8 hours--and provided further insight into the role of CETP as mediator between pools of triglycerides and cholesteryl esters in plasma.

Aged↗
PubMed1997

[Coronary angiography].

Coronary angiography continues to be the standard for assessing coronary artery obstructive disease. Coronary angiography is used not only in diagnosis, but also to assess the appropriateness and feasibility of various forms of therapy. In addition, information provided by coronary angiography is useful for assessing prognosis in patients with coronary artery disease. It helps to decide, whether percutaneous coronary angioplasty, coronary bypass surgery or medical treatment should be performed. Bypass surgery has been shown to improve prognosis in patients with left main and three vessel disease. However, in patients with single vessel disease, choice of therapy generally does not influence prognosis. Although the overall risk of coronary angiography is very low, it should be restricted to patients in whom the information obtained is expected to improve management.

Angioplasty, Balloon, Coronary↗
PubMed1996

Predictors of the presence and extent of peripheral arterial occlusive disease.

BACKGROUND: Data relating lipids to the angiographic presence and extent of atherosclerosis, as reported for the coronary circulation, are lacking for the peripheral site. METHODS AND RESULTS: This study comprised 102 patients with peripheral arterial occlusive disease (PAOD) referred for elective percutaneous transluminal angioplasty and 100 age-matched control subjects with normal coronary and peripheral angiograms. The presence of PAOD was defined as > or = 1 stenosis with > or = 50% narrowing, and the extent was defined as the total of > or = 50% lesions in the iliac, femoral, popliteal, and crural beds. The relation of lipids and nonlipid risk factors to the presence of PAOD was tested by stepwise logistic regression analysis; their relation to the extent of disease was analyzed by simple regression and stepwise discriminant analysis. The presence of PAOD was significantly and positively associated with LDL cholesterol (P = .0003), triglycerides (P = .0001), apolipoprotein B (P = .0073), and smoking (P = .005) and was significantly and negatively associated with HDL2 cholesterol (P = .0085) and apolipoprotein A-I (P = .021). In the logistic model, LDL cholesterol, triglycerides, smoking, and systolic blood pressure were selected as independent predictors of PAOD presence. The extent of PAOD was significantly and negatively correlated with HDL3 cholesterol (P = .005), HDL cholesterol (P = .013), and apolipoprotein A-I (P = .021) and was significantly and positively associated with smoking and fasting blood glucose. Age, smoking, and blood glucose were selected by the discriminant analysis as independent predictors of the extent of PAOD. CONCLUSIONS: From this large case-control study, it is concluded that the presence of PAOD is predicted by parameters of LDL, triglyceride, and HDL2 metabolism, whereas the extent of PAOD is related to HDL3 and nonlipid risk factors.

Adult↗
PubMed1996

[Anti-thrombosis therapy following coronary stent implantation].

Coronary stenting has proved effective in the management of acute or imminent vessel closure after coronary balloon angioplasty. Stent implantation has also been shown to reduce the rate of restenosis. Opposing these benefits, subacute thrombotic stent occlusion is a serious and life-threatening complication which occurred at alarmingly high rates in early series. This paper reviews the contemporary strategies in the prevention of stent thrombosis, emphasizing improved procedural technique and optimal antiplatelet therapy. It is shown that these new preventive strategies led to acceptable subacute stent thrombosis rate of < or = 1%.

Anticoagulants↗
PubMed1996

Are there stereoselective electrophysiologic effects of intravenously administered (S)- or (R)-propafenone hydrochloride in patients with supraventricular tachycardia?

OBJECTIVE: The electrophysiological effects of intravenously administered pure (S)- and (R)-propafenone hydrochloride has been determined for the first time in humans-12 patients with supraventricular tachycardia. METHODS: Measurements were performed before and during drug therapy. RESULTS: (S)- and (R)-propafenone prolonged the AH interval from 82 to 107 ms and 75 to 84 ms, respectively, and significantly increased the V nodal Wenckebach cycle length by 58 ms and 37 ms, respectively. The AV nodal effective refractory period in both groups was increased significantly to the same extent (45 vs 42 ms). Sinus node recovery times were not significantly influenced by either enantiomers. Both (S)- and (R)-propafenone significantly prolonged the HV interval to the same extent (from 41 to 51 ms, and 42 to 53 ms). Changes in the electrophysiological characteristics of the myocardium were more pronounced in the atria than in the ventricles. Only (S)-propafenone significantly increased the atrial effective refractory period from 204 to 230 ms, and the ventricular effective refractory period from 225 to 241 ms compared to (R)-propafenone (from 221 to 239 ms, and from 219 to 222 ms, respectively). There was a more pronounced electrophysiological effect on AV nodal conduction of (S)- than (R)-propafenone, probably as a result of its beta-blocking activity. CONCLUSION: The electrophysiological effects of (S)-compared to (R)-propafenone were not very pronounced, so it still remains questionable whether one of the enantiomers might be clinically superior to the other, or to the racemic mixture.

Adult↗
PubMed1996

[Analysis of early and late results of surgically treated Wolff-Parkinson-White syndrome].

The results of surgical procedures for termination of Wolff-Parkinson-White (WPW) Syndrom were assessed in 59 patients undergoing operation between January, 1980 and December, 1993. All cases of WPW were refractory to medical treatment and 14 of 58 patients had one or several syncopes, and 4 of them had to be reanimated. The surgical treatment of these patients was a dissection of an accessory atrioventricular pathway. 15 patients required additional heart operation. A total of 60 accessory pathways were diagnosed preoperatively, 64 were located intraoperatively. The reoperation rate was 3% (2 patients) due to persistent WPW. Incidence of total AV block after the operation was 7% (4 patients). In the late postoperative stage, 12 patients developed supraventricular tachycardias, but none of these cases required a surgical treatment. The actuarial survival rate after 10 years was 100% and after 14 years 96%. We conclude that surgical dissection of accessory pathways offers a good alternative in cases of unsuccessful catheter ablative procedure or in cases of additional heart operation.

Adolescent↗
PubMed1995

[Hyperventilation test: a noninvasive screening test for coronary vasospasm].

3 patients with coronary vasospasms in different clinical situations are presented. One patient had typical Prinzmetal angina but coronary arteries without significant stenosis. One patient without typical angina pectoris showed sudden significant ST elevations on anterior and lateral ECG tracings accompanied by typical ischemic chest pain. At angiography, a 70% LAD stenosis was found without high degree lesions. One patient (aged 30 years) had a documented anterior infarction with angiographically normal coronary arteries. In all these cases coronary vasospasms were recognized as the underlying cause of the symptoms. All the patients were treated with calcium channel blockers and have been asymptomatic since. Currently available data comparing the diagnostic value of hyperventilation with other tests for coronary vasospasms, such as ergonovine or acetylcholine, are discussed. The hyperventilation test can be recommended as the first test in the work up of suspected vasospastic angina pectoris.

Adult↗
PubMed1995

The internal mammary artery malperfusion syndrome: incidence, treatment and angiographic verification.

Internal mammary artery (IMA) malperfusion syndrome is caused by an acute imbalance between myocardial demand and nutritional support through the mammary artery. In a consecutive series of 2326 isolated myocardial revascularizations-with at least one IMA to the left anterior descending branch (LAD) in 91.3% (2125/2326)-we identified 45 patients (1.9%) with a perioperative course suggesting IMA malperfusion syndrome. Additional saphenous vein graft to the distal segment of the LAD was performed during normothermic ventricular fibrillation in all patients. Hospital mortality was 4.4% (2/45), intra-aortic balloon pumping was required in 15.5% (7/45) and anterior myocardial infarction occurred in 28.8% (13/45). Coronary angiography was performed in all survivors between 3 and 24 months postoperatively. Wide patent IMA graft and patent saphenous vein graft were observed in 56% (24/43), narrowed but patent IMA graft and patent vein graft in 35% (15/43), while patent vein graft and not visualized IMA in 7% (3/43); in one patient with severely diseased peripheral LAD, no flow could be demonstrated in the IMA graft or in the additional vein graft (1/43, 2.4%). No major differences were found between early and late coronary angiography in these patients. Additional vein graft to distal LAD is the treatment of choice in acute IMA malperfusion syndrome. Despite patent vein graft with superior blood flow, early and late postoperative IMA flow to LAD is maintained in the majority of patients.

Adult↗