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Biomedical subjects

U Mehlhorn

Publications and source records attributed to U Mehlhorn.

At least 19 recordsLinked to original sources
PubMed2005

[Is measuring by portable heart rate monitors (sport watches) dependable in patients with an implanted pacemaker?].

BACKGROUND AND OBJECTIVE: Regular physical exercise is advantageous for physical fitness and endurance. The intensity of exercising can be controlled by portable heart rate monitors. The aim of the study was to investigate if wearable monitors work properly in pacemaker patients. PATIENTS AND METHODS: In 30 patients with an implanted single or dual chamber pacemaker made by five different manufacturers their heart rate was determined simultaneously by surface ECG and Holter ECG, and was compared with the heart rates derived from portable heart rate monitors (Polar A1) at rest, during 6 minutes in-house walk, and while exercising at 25, 50, and 75 watts in a bicycle exercise test. The tests were done with pacing set at uni- as well as bipolar stimulation mode. RESULTS: At rest in two of 30 patients (6,6 %) paced in unipolar mode the portable heart rate monitors counted double. Under exercise conditions the portable monitors counted double in six of 26 patients (23 %) while being stimulated in unipolar mode. In bipolar stimulation mode, the portable heart rate monitors were working properly in all patients under all conditions. CONCLUSIONS: Patients with an implanted bipolar pacing system can control their physical exercising safely and accurately by means of portable heart rate monitors. Pacemaker patients who are planning regular physical exercising should be provided with an implanted bipolar pacemaker system.

Adult↗
PubMed2005

Risk stratification models fail to predict hospital costs of cardiac surgery patients.

BACKGROUND: The aim of this prospective study was to determine if commonly used risk stratification models can predict total hospital costs in cardiac surgical patients. METHODS: Between October 1st and December 31st 2003, all consecutive adult patients undergoing cardiac surgery on CPB at our institution were classified using seven risk stratification scoring systems: EuroSCORE, Cleveland, Parsonnet, Ontario, French, Pons, and CABDEAL. Total hospital costs for each patient were calculated on a daily basis including preoperative diagnostic tests, operating room costs, disposable materials, drugs, blood components, costs for personnel, and hospital fixed-costs. Linear regression analysis was used to determine the correlation between costs and the seven risk stratifications models as well as length of stay (LOS) on ICU. The Spearman correlation coefficient was calculated from the regression line, and an analysis of residuals was performed to determine the quality of the regression. RESULTS: A total of 252 patients were operated for CABG (n=175), valve (n=39), CABG plus valve (n=21), thoracic aorta (n=13) and miscellaneous (2 myxoma, 1 ASD, 1 pulmonary embolism). Mean age of the patients was 66.0+/-11.4 years, 29.4% were female. LOS on ICU was 3.3+/-6.3 days and the 30-day mortality rate was 6.7%. Spearman correlation between the seven risk stratification models and hospital costs was below r=0.32 (p=0.0001), but was r=0.94 (p=0.0001) between ICU LOS and costs. CONCLUSIONS: Total hospital costs can be identified by length of ICU stay. None of the common risk stratification models accurately predicted total hospital costs in cardiac surgical patients.

Aged↗
PubMed2005

VDD-pacemaker in children--a long-term therapy?

AIMS: Transvenous AV-synchronous pacing in children started with the invention of smaller sized VDD leads and miniaturization of pacemakers. Whether or not this is a favourable long-term therapy was retrospectively investigated by us based on data from our records. METHODS: From May 1977 to July 2001 we implanted pacemakers in 104 children younger than 15 years of age. In 55 patients transvenous leads were implanted. Twelve of these (21.8 %) received a VDD pacemaker for hemodynamic reasons. RESULTS: Ages ranged from 11 months to 14.5 years (mean 7.7 +/- 4.3 y). Sizes of the children ranged from 67 to 141 cm (mean 105.9 +/- 15.5 cm) and body weight ranged from 5.3 to 62.0 kg (mean 22.5 +/- 9.8 kg). The mean follow-up period was 47.5 +/- 15.1 months. In 86.3 % of the time during follow-up pacemakers of which we obtained data were working in the VDD mode. Five of the twelve VDD patients (41.7 %) had to be reoperated because of severe traction on the leads. In all five patients the VDD systems were explanted and the patients changed to dual chamber pacemakers. The period of time between implantation and VDD lead explantation ranged from 24 to 74 months (48.6 +/- 18.5). CONCLUSIONS: VDD pacemakers can be implanted safely even in children with a low complication rate perioperatively. 41.7 % of our VDD patients had to be reoperated within the surveillance time because of severe lead tension due to thoracic growth. In our experience VDD pacemakers in smaller children seem to be a temporary solution to bridge AV-synchrony from a young age to DDD pacing in young adulthood.

Child↗
PubMed2004

[S2 guideline for infectious endocarditis].

Microbe-induced (infectious) endocarditis is an endovascular infection, caused mainly by bacteria, of cardiovascular structures. The major predilection site are the native heart valves, but involvement of implanted intracardiac foreign material is increasingly being seen. The mortality rate of infectious endocarditis depends on clinical factors and the causal agent, but also on the time of the establishment of the diagnosis and the initiation of appropriate treatment. In Germany, the current mortality rate ranges up to 18%. Between January 2003 and July 2004, with the aim of improving patient care and thus the outcome of this condition, a guideline commission worked out recommendations for the diagnosis, treatment and management of the disease for the use of general practitioners and hospital physicians, in particular microbiologists, infectiologists, cardiologists and cardiac surgeons. The basis for this guideline was the systematic search through the literature of the European guideline. On the 16th and 28th of June 2004, the entire guideline was formerly approved in a nominal group process.

Anti-Bacterial Agents↗
PubMed2004

Interference by cellular phones with permanent implanted pacemakers: an update.

AIMS: The aim of this study was to test pacemakers with feedthru filters for interference with a digital cellular telephone. METHODS: The study comprised 100 patients having their first pacemaker implantation between January 2001 and May 2003. A GSM-standard cellular phone was tested in the standby, dialing and operating mode against 23 single-chamber and 77 dual-chamber pacemakers. Continuous surface electrocardiograms, intracardiac electrograms, and marker channels were recorded when calls were made by a land phone to the cellular phone. RESULTS: In 2 patients we observed pacing inhibition with the cellular phone positioned directly above the pacemaker pocket. The unipolar and bipolar ventricular sensitivity setting was 0.25 mV in one dual-chamber pacemaker, and when we changed the sensitivity to 0.50 mV and higher no interference could be detected. The second inhibition occurred in a single-chamber pacemaker with unipolar and bipolar ventricular sensitivity setting of 0.5 mV, where a sensitivity change to 1.0 mV eliminated the interference. CONCLUSION: Anticipating a correct setting of ventricular sensitivity, currently available pacemakers equipped with feedthru filters do not show any interference with cellular phones. Since interference was only observed with sensitivity settings below 0.50 mV, we recommend that permanent programming of ventricular sensitivity should be set at 2.0 mV and higher.

Adolescent↗
PubMed2004

Impact of tranexamic acid vs. aprotinin on blood loss and transfusion requirements after cardiopulmonary bypass: a prospective, randomised, double-blind trial.

INTRODUCTION: Aprotinin (AP) reduces blood loss and transfusions after cardiopulmonary bypass (CPB), but may sensitise patients and is expensive. Tranexamic acid (TA) has less side-effects, but data regarding its efficacy are controversial. The aim of our prospective, randomised, double-blind study was to compare the impact of AP vs. TA on drainage blood loss and transfusion requirements in patients undergoing first time CABG on CPB. MATERIALS AND METHODS: One hundred and twenty adult patients were randomised to receive either high-dose AP according to Hammersmith or a total of 2 g TA. Perioperative blood products were transfused in a standardised fashion. Blood loss was measured up to 24 h. Demographic and clinical patient data were collected until hospital discharge. RESULTS: The data from 118 patients (TA: n = 58, AP: n = 60) who completed the study according to protocol were analysed. Blood loss at 24 h postoperation in TA patients was significantly higher (896 +/- 354 ml) as compared to AP patients (756 +/- 347 ml; p = 0.03). TA patients received 1.5 +/- 1.5 units of red blood cells (AP: 1.5 +/- 1.7, p = 1.0), 1.3 +/- 2.0 units of fresh frozen plasma (AP: 1.0 +/- 2.0, p = 0.38) and 0.5 +/- 1.4 units of platelets (AP: 0.2 +/- 0.7, p = 0.15). Clinical data, including perioperative myocardial infarction rate, acute renal failure, mechanical ventilation, hospital stay and mortality, were not significantly different between either group. CONCLUSION: Our data show a difference in blood loss between TA and high-dose AP. Although statistically significant, it has little clinical relevance, because perioperative transfusion requirements were similar for both groups. Thus, TA appears to be a cost-effective alternative to AP in primary CABG patients.

Antifibrinolytic Agents↗
PubMed2004

The effect of preoperative antiplatelet therapy in coronary artery surgery: blood transfusion requirements for patients on cardiopulmonary bypass.

INTRODUCTION: Bleeding after heart operations remains a common complication and contributes to morbidity and death. Recent studies have suggested that antiplatelet therapy (APT) may not increase homologous blood requirements in coronary bypass surgery. The purpose of this study was to examine the influence of APT therapy on haemorrhage and transfusion requirements in patients undergoing coronary artery bypass (CABG) on cardiopulmonary bypass (CPB). MATERIALS AND METHODS: Records from 290 consecutive patients who underwent CABG with CPB were retrospectively reviewed, including 145 patients who received APT within 5 days prior to surgery and 145 control patients (CON). Blood loss was measured up to 24 h. Demographic and clinical patient data were collected until hospital discharge. RESULTS: Both groups were well matched with respect to demographic and intra-operative data. There was significantly (p < 0.0005) more mediastinal tube drainage at 24 h in the APT group (1123 mL +/- 537 mL) compared to CON patients (874 mL +/- 351 mL). In addition, the APT group received significantly more units of blood (APT: 2.6 +/- 2.5 vs CON: 1.6 +/- 1.8; p < 0.0005), platelet units (APT: 1.2 +/- 1.8 vs CON: 0.2 +/- 0.8; p < 0.0005), and fresh frozen plasma units (APT: 2.0 +/- 2.2 vs CON: 1.3 +/- 2.0; p = 0.01). CONCLUSION: This study suggests consideration should be given to delaying elective CABG for patients who have received APT treatment until APT is discontinued for at least 5 days.

Blood Loss, Surgical↗
PubMed2003

The preferential beta3-adrenoceptor agonist BRL 37344 increases force via beta1-/beta2-adrenoceptors and induces endothelial nitric oxide synthase via beta3-adrenoceptors in human atrial myocardium.

1 The present study investigated the effects of the preferential beta(3)-AR agonist BRL 37344 (BRL) on force of contraction (FOC), Ca(2+)-transient and eNOS-activity in human right atrial myocardium. 2 BRL concentration-dependently caused an increase in FOC that was paralleled by an increase in Ca(2+)-transient and a shortening of time to half peak relaxation (T0.5T). These effects were abolished in the presence of propranolol (0.3 micro M). 3 BRL acted as a competitive antagonist towards isoprenaline and in binding experiments it was shown to have a distinct affinity towards beta(1/2)-AR. 4 In immunohistochemical experiments BRL (10 micro M) increased detection of activated eNOS. This effect remained constant in the presence of propranolol (0.3 micro M). 5 BRL increased directly detected NO in DAF-staining experiments. This increase was significantly smaller in the presence of the NO-inhibitor L-NAME. 6 The inotropic effects of BRL were not changed in the presence of L-NMA. 7 These results suggest that the inotropic effects of BRL in human atrium are mediated via beta(1/2)-AR, whereas the increase of atrial eNOS-activity is due to beta(3)- adrenergic stimulation. This increase in eNOS-activity did not influence atrial myocardial contractility. In conclusion, this study shows that beta(3)-adrenergic stimulation is present in human atrium, but may not be functionally as significant as in the left ventricle.

Adrenergic beta-Agonists↗
PubMed2003

Transvalvular in vivo gradients of the new generation bileaflet heart valve prosthesis St. Jude Medical Regent in aortic position.

BACKGROUND: By changing the design of the St. Jude Medical Regent prosthesis in shifting both sewing cuff and retaining ring into a completely supra-annular position, the Regent valve has a greater geometric orifice for a given outer diameter. Accordingly, in vitro studies have shown increased effective orifice areas (EOAs) and lower transvalvular gradients. The aim of our study was to determine in vivo transvalvular gradients and EOAs in patients after aortic valve replacement (AVR). METHODS: We investigated 75 patients at 12 to 21 months follow-up after AVR using transthoracic echocardiography. We determined left ventricular systolic and diastolic function, EOA, and transvalvular peak gradient parameters at rest. Outcomes were assessed using the NYHA classification and functional status. RESULTS: No patient experienced cardiac failure. The majority reported good functional status and good quality of life. Five (6.7 %) late deaths were observed within the surveillance period. At follow-up, 92 % of the patients had improved by at least one NYHA class. Transvalvular peak gradients at rest for patients with Regent valves were 25.4 +/- 7.7 mmHg, 19.2 +/- 4.6 mmHg, 15.6 +/- 5.8 mmHg, 14.6 +/- 5.5 mmHg, and 8.5 +/- 2.5 mmHg; EOAs were 1.38 +/- 0.32 cm2, 1.62 +/- 0.49 cm2, 2.24 +/- 0.83 cm2, 2.63 +/- 0.70 cm2, and 3.28 +/- 0.34 cm2 for valve sizes 19 mm, 21 mm, 23 mm, 25 mm, and 27 mm, respectively. CONCLUSIONS: The SJM Regent valve shows excellent in vivo hemodynamics as confirmed by echocardiography. Clinically, 92 % of the patients improved by at least one NYHA class.

Aortic Valve↗
PubMed2003

Morphology and density of initial lymphatics in human myocardium determined by immunohistochemistry.

BACKGROUND: Myocardial edema is a common finding in congestive heart failure, transplant rejection, and cardiomyopathy. Although pathological alterations in the lymphatic morphology are part of the underlying disease, knowledge on these changes is limited. However, lymphatic morphology may be investigated by immunohistochemical staining for fms-like tyrosine 4 kinase (flt-4), which is specific for lymphatic endothelium in adult tissue. METHODS: We used myocardial tissue of ventricular out flow tract taken from five human semilunar valves harvested as allografts but unsuitable for implantation for analysis, performing immunohistochemical staining for flt-4 with a commercially available antibody. Lymphatic morphometry was completed according Gundersen method. RESULTS: Immunohistochemical staining for flt-4 resulted in successful labeling of lymph capillaries in adult human myocardium. Lymph capillary density was calculated as 50.7 +/- 12.5 per mm2 and average diameter was 3.7 +/- 0.7 microm. Conclusions. Lymph capillary morphology in human myocardium may be successfully determined by immunohistochemical staining for flt-4. Tissue samples as small as myocardial biopsies may be used for analysis. Using this method, morphological changes in myocardial lymphatics may be investigated in various cardiovascular diseases.

Adult↗
PubMed2002

Cardiopulmonary bypass copolymer surface modification reduces neither blood loss nor transfusions in coronary artery surgery.

OBJECTIVE: Surface-modifying additives (SMA) have been suggested for improving cardiopulmonary bypass (CPB) circuit biocompatibility, potentially minimizing inflammatory complications and bleeding associated with CPB. The purpose of this prospective, randomized clinical study was to compare a novel copolymer surface-modified CPB circuit (SMARXT; COBE Cardiovascular) against the unmodified circuit. METHODS: We randomized 122 patients with isolated coronary artery disease subjected to first-time surgery on CPB into either the SMA (n = 62) or the control group (n = 60). Exclusion criteria included renal insufficiency, liver disease, coagulopathy, anticoagulation therapy < 6 days preop, carotid artery stenosis > 70 %, and a history of stroke. We collected perioperative clinical data including drainage blood loss, transfusion requirements, duration of mechanical ventilation, and ICU stay. Platelet function was determined pre- and post-CPB. RESULTS: SMA patients received 3.2 +/- 0.9 (SD) grafts during 48 +/- 16 min of aortic cross clamp and 91 +/- 30 min CPB (Control: 3.0 +/- 0.9 grafts; p = 0.33, 46 +/- 14 min AXC; p = 0.36, and 84 +/- 23 min CPB; p = 0.14). In the SMA group, 23 patients (37 %) received red blood-cell transfusions, 9 patients (15 %) fresh frozen plasma, and 3 patients (5 %) received platelets (control: n = 27 [46 %], p = 0.44; n = 10 [17 %], p = 0.91; and n=4 [7 %], p = 0.71, respectively). Platelet count on CPB fell to the same level in both groups. In SMA patients, platelet function decreased from 94.2 +/- 24.9 % pre-CPB to 79.5 +/- 32.8 % post-CPB (p = 0.043) (control: from 87.7 +/- 25.6 % to 69.4 +/- 34.7 %; p = 0.001). Postoperative drainage blood loss, mechanical ventilation duration, and ICU stay were similar in both groups (p > 0.3). One patient of the control group was excluded due to surgical bleeding, and one SMA patient died. CONCLUSIONS: Our results show that the surface-modified CPB circuit decreased neither blood loss nor transfusions despite slightly better platelet function preservation compared to the unmodified circuit. This type of CPB circuit surface modification does not appear to improve clinical outcome in low-risk coronary artery surgery patients.

Aged↗
PubMed2002

Beta-blockade in 200 coronary bypass grafting procedures.

BACKGROUND: Continuous perfusion of the coronary arteries with high-dose beta-blocker (esmolol)-enriched blood has been shown to represent an alternative for myocardial protection during coronary bypass grafting (CABG). Here, we will report on our experience in 200 unselected consecutive cases where this technique was used. METHODS: Eighty percent of the patients (age: 63.3 +/- 0.6 years, ejection fraction: 60 +/- 1.2 %, emergency cases: 11 %) had 3-vessel disease, 34 % had a history of myocardial infarction within less than 90 days preoperatively. The Euro score amounted to 6 +/- 0.3. During 52 +/- 1.2 min of aortic cross-clamp time on normothermic cardiopulmonary bypass, 2.9 +/- 0.1 distal anastomoses were performed on a slow hypocontractile beating heart induced by continuous infusion of 788 +/- 20 mg esmolol per operation. All data: mean +/- SEM. RESULTS: Postoperatively, patients were ventilated for 25 +/- 5.1 hours and stayed on ICU for 2.3 +/- 0.3 days. The postoperative myocardial infarction rate was 4%. Patients left the hospital after 11.2 +/- 0.4 days. Thirty-day mortality was 2.5 %, and 3-month mortality was 3 %. CONCLUSIONS: High-dose beta-blockade is a safe and effective technique in CABG procedures. It may be especially advantageous in high-risk patients.

Adrenergic beta-Antagonists↗
PubMed2002

Impact of hematocrit value after coronary artery surgery on perioperative myocardial infarction rate.

BACKGROUND: The optimal hematocrit (HCT) value after coronary artery bypass grafting on cardiopulmonary bypass (CPB) has not yet been established. The purpose of our retrospective study was to investigate the association between HCr at the time of entry into the ICU and perioperative Ml rate. METHODS: We reviewed the charts of 500 consecutive coronary artery surgery patients with respect to biometric data, operative procedure, aprotinin or tranexamic acid use, perioperative drainage blood loss and transfusion requirements, perioperative Ml, ICU stay and hospital mortality. Perioperative Ml was defined as new Q-wave on ECG and CK-MB 250U/I. Patients were categorized into three groups depending on their HCr value at the time of entry into the ICU: low (HCTcu 27%): medium (HCr,cu 28% to 32%); high(HCTrcu > or =33%). RESULTS: Age, gender distribution, preoperative LV function, and previous Ml rate were similar between the three groups. Low HCT patients (n -133) received 3.1 +/- 1.0 (Mean + SD) grafts during 55 +/- 19 minutes aortic cross clamp time, 98 +/- 31 minutes on CPB (medium HCT: n = 257; 3.2 +/- 1.0 grafts, 51 +/- 20 min cross clamp time, 93 +/- 30 min CPB; p - 0.45 vs. low HCT; high HCT: n = 110: 3.3 +/- 1:0 grafts; 53 +/- 20 min cross clamp time; 104 +/- 38 min CPB; p = 0.02 vs. medium HCT). The perioperative Ml rate was 3.8% in the low, 4.3% in the medium, and 6.4% in the high-HCr group (p =0.59 ). Intraoperative red blood cell and fresh frozen plasma transfusions were similar between the groups. In the low-HCa group, 53.4% of the patients received aprotinin during the procedure (medium HCa: 65.4%; high HCT: 77.3%; p<0.001). Drainage blood loss during the first 24 hours on ICU was 834 +/- 453 ml in the low, 757 +/- 485 ml in the medium (p -0.44 vs. low), and 640 +/- 353 ml in the high-HCr group (p = 0.003 vs. low). Postoperative red blood cell and fresh frozen plasma transfusions were highest in the low-HCa group(p<0.001). ICU stay was similar between the groups. Hospital mortality was 0.75% in the low, 1.9% in the medium, and 4.5%in the high-HCa group (p = 0.12). CONCLUSIONS: In this retrospective analysis of 500 consecutive coronary artery surgery patients, we did not find any association between perioperative Ml rate and HCr value on entry into the ICU. These results do not support the recent suggestion that low HCT at the time of entry into the ICU protects against perioperative Ml.

Aged↗
PubMed2001

Nebivolol, carvedilol and metoprolol do not influence cardiac Ca(2+) sensitivity.

It has been argued that some beta-adrenoceptor antagonists may directly influence myofibrillar cross-bridge interaction in cardiac skinned fiber preparations of animal models. The present study investigates the effects of nebivolol, metoprolol and carvedilol on tension development of Triton X-100 skinned fibers obtained from human failing myocardium as well as on force of contraction and intracellular Ca(2+) transient in isolated trabeculae. In skinned fiber preparations, none of the beta-adrenoceptor antagonists (10 microM) influenced Ca(2+) sensitivity of tension development or maximal Ca(2+) activated tension (DT(max)): control: EC(50) for Ca(2+): 1.28+/-0.05 microM, DT(max): 14.09+/-0.59 mN/mm(2); nebivolol: 1.36+/-0.1 microM, 14.14+/-0.95 mN/mm(2); carvedilol: 1.32+/-0.11 microM, 13.83+/-0.90 mN/mm(2); metoprolol: 1.34+/-0.14 microM, 13.72+/-0.36 mN/mm(2). Simultaneous measurement of force and Ca(2+) transient in the presence of the beta-adrenoceptor antagonists (3 microM) showed that the decrease in force of contraction was paralleled by a similar decrease in the intracellular Ca(2+) transient. In conclusion, none of the investigated beta-adrenoceptor antagonists influenced Ca(2+) sensitivity of myofibrillar tension development in human failing myocardium.

Adrenergic beta-Antagonists↗
PubMed2001

Ischemia increases detectable endothelial nitric oxide synthase in rat and human myocardium.

The aims of the present study were to establish if myocardial ischemia/reperfusion is associated with altered eNOS activity and if myocardial eNOS detection depends on its activity. We determined detectable eNOS in (1) myocardium of isolated perfused rat hearts subjected to either global or regional ischemia and (2) in left ventricular biopsies from patients undergoing two different methods of myocardial protection (i.e., intermittent cold blood cardioplegia and continuous coronary perfusion with warm, beta-blocker-enriched blood) during coronary artery surgery. NOS detection was performed by NADPH-d staining and three eNOS-antibodies against different eNOS epitopes. In addition, activity dependent alteration of detectable eNOS was proofed by bradykinin treatment for 2 to 10 min. Ischemic and receptor mediated eNOS activation increased NADPH-d reactivity and eNOS immunoreaction as measured by antibodies against either amino acids of a central bovine eNOS domain or the human eNOS N-terminal end. In contrast, the antibody against the human eNOS C-terminal end exhibited no alteration of eNOS immunoreaction. The transient eNOS activation was associated with increased cGMP content. In human myocardium subjected to ischemia during cardiac surgery we found that early reperfusion increases eNOS activity. These data demonstrate a strong association between myocardial ischemia/reperfusion and increased eNOS activity as measured by immunocytochemical staining against specific eNOS epitopes. It appears that eNOS activation and subsequent NO release may act as a regulatory system to counter balance the potentially deleterious effects of myocardial ischemia/reperfusion.

Adrenergic beta-Antagonists↗
PubMed2001

Esmolol and cardiopulmonary bypass during reperfusion reduce myocardial infarct size in dogs.

BACKGROUND: Infarct size can be reduced by beta-blockade in acute myocardial ischemia. However it is unknown whether myocardial salvage is still effective when beta-blockade is limited to reperfusion. METHODS: After initiation of cardiopulmonary bypass, 20 dogs were submitted to 2 hours of regional left ventricular ischemia, followed by 2 hours of reperfusion. In 11 dogs beta-blockade was started with the onset of reperfusion (esmolol group). The remaining dogs received no treatment (control, n = 9). Infarct size was determined by tetrazolium chloride staining. Myocardial water content (MWC) and ultrastructural damage (electronmicroscopy) were determined from transmural biopsies. RESULTS: Infarct size was significantly smaller in the esmolol group compared with control (49% versus 68%, p < 0.05). After 2 hours ischemia there was no difference in MWC between groups, whereas after 2 hours reperfusion MWC of ischemic myocardium was significantly lower in the esmolol group than in the control (p < 0.05). Ultrastructural changes were typical for ischemia-reperfusion injury in both groups. CONCLUSIONS: Beta-blockade may be cardioprotective during reperfusion through various mechanisms and may enhance myocardial salvage, even when treatment is initiated as late as with the onset of reperfusion.

Adrenergic beta-Antagonists↗
PubMed2001

Effects of chronic atrial fibrillation on gap junction distribution in human and rat atria.

OBJECTIVES: To elucidate the structural basis for the electrophysiologic remodeling induced by chronic atrial fibrillation (AF), we investigated connexin40 and connexin43 (Cx40 and Cx43) expression and distribution in atria of patients with and without chronic AF and in an animal model of AF with additional electrophysiologic investigation of anisotropy (ratio of longitudinal and transverse velocities). BACKGROUND: Atrial fibrillation is a common arrhythmia that has a tendency to become persistent. Since gap junctions provide the syncytial properties of the atrium, changes in expression and distribution of intercellular connections may accompany the chronification of AF. METHODS: Atrial tissues isolated from 12 patients in normal sinus rhythm at the time of cardiac surgery and from 12 patients with chronic AF were processed for immunohistology and immunoblotting for the detection of the gap junction proteins. The functional study of the cardiac tissue anisotropy was performed in rat atria in which AF was induced by 24 h of rapid pacing (10 Hz). RESULTS: Immunoblotting revealed that AF did not induce any significant change in Cx43 content in human atria. In contrast, a 2.7-fold increase in expression of Cx40 was observed in AF. Immunohistologic analysis indicated that AF resulted in an increase in the immunostaining of both connexins at the lateral membrane of human atrial cells. A similar spatial redistribution of the Cx43 signal was seen in isolated rat atria with experimentally-induced AF. In addition, AF in rat atria resulted in decreased anisotropy with slightly enhanced transverse conduction velocity. CONCLUSIONS: This experimental study showed that AF is accompanied by spatial remodeling of gap junctions that might induce changes in the biophysical properties of the tissue.

Aged↗