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Biomedical subjects

H Mächler

Publications and source records attributed to H Mächler.

26 records · Page 2Linked to original sources
PubMed1995

Adenosine inhibits the L-type calcium current in human atrial myocytes.

The effects of adenosine on the L-type Ca2+ current (Ica) were studied in human atrial myocytes using the whole-cell voltage clamp technique. Ica was recorded under physiological calcium concentrations (1.8 mmol/l) at 37 degrees C. Under these conditions the current density of basal Ica averaged 4.0 pA/pF. Isoprenaline (1 mumol/l) increased basal Ica to 249.7%. Adenosine (100 mumol/l) in the presence of isoprenaline (1 mumol/l) decreased Ica from the level obtained with isoprenaline to 87.5% of basal Ica. Adenosine (0.1 to 100 mumol/l) also reduced basal Ica, maximally to 64.5% of control. Activation and inactivation parameters of basal Ica were not significantly different between adenosine (100 mumol/l) and control recordings. Our results show that adenosine affects both basal and isoprenaline stimulated Ica in human atrial myocytes. Although a considerable decrease of basal Ica was seen, we conclude that the action of adenosine on L-type Ca2+ current in human atrial myocytes is mainly antiadrenergic. Both effects may contribute to the antiarrhythmic properties of adenosine.

Acetylcholine↗
PubMed1995

[Total cavo-pulmonary connection as a therapeutic principle in anatomical and functional univentricular heart].

The original Fontan operation was employed for patients with tricuspid atresia, but its application has been extended to a broad spectrum of congenital cardiac defects with a functional or anatomical single ventricle. From 1989 to 1995, 35 patients (23 males, 12 females) underwent a modified Fontan procedure; their age ranged from 14 months to 15 years (mean 5.1 a). Indications for operation were the following: D(S)ILV = 16, TA = 9, MA = 3, TGA with straddling AV-valve = 2, DORV = 4 and criss-cross heart = 1. The same surgical technique was utilized in all patients with redirection of the systemic venous return by means of a bidirectional cavopulmonary anastomosis and an intraatrial baffle, adaptable to all the various forms of underlying anatomy. Associated anomalies such as dextrocardia, coarctation, anomalous systemic or pulmonary venous return, subaortic stenosis and situs anomalies were present in 26%, 9%, 26%, 9%, and 20%, respectively. 12 patients were presumed to be at high risk and underwent a two-stage procedure (n = 7 bidirectional Glenn preceding the definitive repair and n = 5 a fenestration of the intraatrial baffle). Risk factors in our group of patients were: age under 2 years, abnormal systemic venous drainage, stenotic pulmonary arteries, PVR over 2 Wood units, mPAP over 15 mmHg, AV-valve incompetence, subaortic obstruction and ventricular dysfunction. Two patients had failure of the total cavo-pulmonary connection necessitating the take-down to a bidirectional Glenn anastomosis in the early postoperative period, with one death. Hospital mortality was 24% (n = 8). One child did not survive complications following the fenestration closure 4 months postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Troponin T as a marker of perioperative myocardial cell damage.

Unstable angina in patients undergoing CABG surgery is associated with a higher morbidity and mortality compared to patients with stable angina. Mortality ranges between 2 and 10% (20, 21). The importance of the preoperative status is only clear and well documented for patients with unstable angina who are unresponsive to medical treatment, patients who undergo emergency revascularization, and for patients with failed angioplasty. The adverse outcome in elective patients with unstable angina was statistically not significantly different from those with stable angina. Therefore, we may assume that in stabilized patients with unstable angina and minor myocardial cell damage intraoperative determinants like the duration of the aortic clamping period or the degree of revascularization are more relevant than the preoperative ones. These determinants may also be reflected by a marked and significant increase of troponin T in both groups during and after surgery. As for other cardiac enzymes, this increase of troponin T beginning immediately after reperfusion of the cardioplegic heart may limit its diagnostic value after cardiac surgery (6,22). On the other hand, troponin T may serve as a marker in assessing the effectiveness of different cardioprotective measures. Nevertheless, preoperatively elevated troponin T levels may indicate a jeopardized myocardium with an ongoing process of myocardial cell damage and may be of prognostic value. Antianginal and antiischemic therapy, therefore, has to be continued and completed until the day of surgery in these high-risk patients.

Angina, Unstable↗
PubMed1994

Preoperative myocardial cell damage in patients with unstable angina undergoing coronary artery bypass graft surgery.

BACKGROUND: Troponin-T is one of the contractile proteins of the myocardium. Its release into the circulation indicates various degrees of myocardial cell damage. Troponin-T may be measured in serum with a recently developed enzyme immunoassay. This immunoassay was used to evaluate the preoperative myocardial cell damage in patients with stable and unstable angina undergoing elective coronary artery bypass graft surgery, and it was compared with conventional assays of creatine kinase (CK) MB isoenzyme activity and mass. METHODS: Twenty-one patients with unstable angina and 31 with stable angina were studied. Troponin-T, CK-MB activity, and CK-MB mass were measured 24 h before anesthesia and surgery, immediately before induction of anesthesia, before and after cardiopulmonary bypass, at the end of surgery, and 24 h afterward. RESULTS: In 90% (19 of 21) of the patients with unstable angina, troponin-T was increased 24 h before anesthesia (median 0.33 microgram/l, range 0.15-5.2 micrograms/l), whereas only 3% (1 of 31) of the patients with stable angina had increased values (median 0.0 microgram/l, range 0.0-0.53 microgram/l). The difference was statistically significant (P < 0.001). The same profile was found in patients with and without unstable angina immediately before induction of anesthesia (86% [18 of 21] and 0%, respectively) and before cardiopulmonary bypass (62% [13 of 21] and 0%, respectively). In contrast to troponin-T, CK-MB activity was increased in only 0-14% of patients with unstable angina, and CK-MB mass was increased in only 9-24%. After bypass troponin-T increased in both groups (P < 0.01), but there was no longer a statistically significant difference between the groups. Twelve percent (4 of 31) of the patients in the stable angina group and 28% (6 of 21) in the unstable group had major cardiac events (P not significant). CONCLUSIONS: The study data suggest that many patients with unstable angina undergoing elective coronary artery bypass graft surgery have already increased troponin-T levels preoperatively, although conventional biochemical markers such as CK-MB activity and mass are at a normal range. Increased troponin-T and normal CK-MB concentrations may reflect some degree of ischemic myocardial cell damage. Because of the small number of patients in the study, the influence of preoperative myocardial injury on perioperative outcome could not be clarified.

Adult↗
PubMed1993

Brain magnetic resonance imaging in coronary artery bypass grafts: a pre- and postoperative assessment.

We undertook a study to determine (1) the frequency and prognostic significance of preexisting MRI brain abnormalities in patients undergoing coronary artery bypass grafts (CABG) and (2) whether MRI can detect surgery-related brain damage in 31 neurologically asymptomatic CABG patients (mean age, 61.0 +/- 6.6 years). MRIs were performed within 7 days before and 8 to 17 days after surgery. When we compared the preoperative images with those of 31 age- and risk factor-matched neurologically asymptomatic controls free of cardiac disease (mean age, 60.3 +/- 6.1 years), higher rates of thromboembolic infarcts (16% versus 0%), lacunes (58.1% versus 32.3%), and brainstem lesions (22.6% versus 3.8%) were noted. Subjective rating demonstrated significantly larger ventricles in patients than in controls (p = 0.002). CABG candidates also had significantly increased ventricular-to-intracranial cavity ratios (VICR) as determined by semiquantitative volumetric measurements (6.9 +/- 2.5% versus 4.9 +/- 1.6%; p = 0.0004). Eleven patients had postsurgical complications, with eight having symptoms consistent with diffuse encephalopathy. The only MRI finding that separated encephalopathic from complication-free patients was ventricular size (VICR 9.0 +/- 2.5% versus 4.9 +/- 1.6%; p = 0.006). This difference remained statistically significant after adjustment for the effects of age (p = 0.04). Postoperative MRI consistently failed to demonstrate surgery-related brain damage responsible for the encephalopathy.

Aged↗
PubMed1987

Mitral atresia with premature closure of the oval foramen, right-sided levoatriocardinal vein and thrombus formation in the left atrium.

We describe a 4-week-old baby with mitral atresia, hypoplastic left ventricle, ventricular septal defect, preductal coarctation and premature closure of the oval foramen whose only outlet from the left atrium was a stenosed right-sided levoatriocardinal vein and who in addition developed left atrial thrombi. Cross-sectional echocardiography was extremely helpful in establishing the diagnosis.

Abnormalities, Multiple↗