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Biomedical subjects

O C Penn

Publications and source records attributed to O C Penn.

At least 37 records · Page 2Linked to original sources
PubMed1991

Canine-specific adaptation of energy metabolism of latissimus dorsi muscle in response to chronic electrical stimulation.

Continuous electrical stimulation ot canine latissimus dorsi (LD) muscle in situ during 24 weeks induced an increase of immunohistochemically assayed type I fibers from about 30 to 80%. Concomitantly, the activity of fructose-6-phosphate kinase, a key enzyme of the glycolytic pathway, declined markedly, but the capacity for fatty acid oxidation remained unaltered. With respect to myofibrillar and metabolic properties the dog LD muscle initially resembled soleus muscle, and after 24 weeks of stimulation had acquired the properties of gastrocnemius muscle. It is concluded that in the dog, unlike the rat, the LD muscle has an inherently fixed capacity for oxidative energy production. Further expansion of its resistance to fatigue, as induced by chronic stimulation, most likely results mainly from a more efficient coupling between tension development and energy production.

Adaptation, Physiological↗
PubMed1990

[Cardiomyoplasty: a new alternative in chronic heart failure].

The technique of cardiomyoplasty to support the failing heart as applied in the first two patients in The Netherlands is reported. Indications are presented for the selection of patients who might benefit from a cardiomyoplasty procedure, considering its experimental nature.

Cardiac Surgical Procedures↗
PubMed1990

Reversibility of tachycardia-induced cardiomyopathy after cure of incessant supraventricular tachycardia.

Seven of 17 patients with incessant supraventricular tachycardia caused by an accessory pathway with a long retrograde conduction time were seen with symptoms or echocardiographic signs of a tachycardia-induced cardiomyopathy. Three patients were in New York Heart Association functional class II with dyspnea and four were in class III. Eight patients (six with tachycardia-induced cardiomyopathy) underwent surgery because of failure of medical treatment (including one patient in functional class I) and one underwent direct current catheter ablation of the atrioventricular (AV) node. In six patients echocardiograms recorded before and after the procedure were available. Before surgery or direct current ablation the mean left ventricular ejection fraction was 36.3 +/- 8.7%, the left ventricular end-diastolic diameter 55.7 +/- 7.6 mm and the left ventricular end-systolic diameter 44.3 +/- 7.8 mm. A mean of 21.6 +/- 6.8 months after the procedure the mean left ventricular ejection fraction increased to 58.6 +/- 8.0%, the left ventricular end-diastolic diameter decreased to 49.0 +/- 3.6 mm and the left ventricular end-systolic diameter decreased to 32.2 +/- 2.7 mm; all six patients were in functional class I. These results confirm that control of incessant tachycardia leads to a regression of symptoms and signs of cardiomyopathy and progressive normalization of the dimensions of the heart. Because of these findings, surgery should be considered early in patients with an accessory AV pathway and incessant tachycardia. The presence of a tachycardia-induced cardiomyopathy should therefore be an indication for surgery rather than a contraindication.

Adult↗
PubMed1990

Giant intrapericardial aneurysm of the left atrial appendage.

A young patient is reported with an aneurysm of the left atrial appendage having supraventricular arrhythmias and a period of chest pain accompanied by a rise in cardiac enzymes. Compression of the left anterior descending coronary artery by the aneurysm was felt to be responsible for the myocardial injury.

Adolescent↗
PubMed1990

An artificial neural network to localize atrioventricular accessory pathways in patients suffering from the Wolff-Parkinson-White syndrome.

UNLABELLED: The electrocardiographic localization of atrioventricular accessory pathways has been extensively described in the literature by a number of well-known electrophysiologists and surgeons. These descriptions, often represented as decision trees, are useful, but do not apply in all cases. To formalize the process of determining the proper localization, this expert human knowledge could be represented in an expert system. But since reasoning is partly based on the use of heuristic knowledge, and are often not represented in the written description of the human expert, the results will be suboptimal. On the other hand, by using a self-learning neural network approach, the causal relations between input (polarity of the delta waves) and output (the correct localization) do not have to be defined by the expert. It is derived by the neural network, by analyzing a learning set of cases consisting of the ECG plus the corresponding correct localization. In our set of 60 cases, 2 hours of training were required to learn how to localize all cases correctly. From a control set of 25 cases, 23 were interpreted by the system satisfactorily. CONCLUSION: the neural network approach can be useful in situations where causal relations between the electrocardiogram and underlying mechanism are partly undefined.

Artificial Intelligence↗
PubMed1990

Diagnosis and treatment of patients with accessory pathways.

Of the accessory pathways, partially or totally bypassing the atrio-ventricular conduction system, the bundle of Kent is the most common type. The electrocardiographic (ECG) expression of preexcitation depends upon the contribution of the activation fronts over the AV node and the accessory pathway. From the polarity of the delta wave in the surface ECG and from the behavior during electrophysiologic study, the location of the accessory pathway can be derived. The presence of an accessory pathway may induce circus movement tachycardia and, in case of atrial fibrillation, high ventricular rates possibly leading to sudden death. Noninvasive techniques are able to identify the patient at high risk. Treatment modalities are pharmacologic or surgical, whereas ablation techniques are still under investigation.

Anti-Arrhythmia Agents↗
PubMed1989

Angiographic and clinical characteristics of patients with unstable angina showing an ECG pattern indicating critical narrowing of the proximal LAD coronary artery.

One hundred eighty of 1260 patients consecutively admitted to the hospital because of unstable angina pectoris had the typical ST-T segment changes suggestive of a critical stenosis in the proximal LAD. In 108 patients the ECG abnormalities were present at the time of admission. In the remaining 72 patients they developed shortly thereafter. The difference between these two groups was a longer duration of anginal complaints in the former (mean 2.3 days). Results of coronary angiography, performed a mean of 4.6 days after the last attack of chest pain, showed 50% or more narrowing in the proximal LAD in all patients. Thirty-three patients had complete occlusion of the LAD and 75 had collateral circulation to the LAD. Results of left ventricular angiography showed abnormal systolic left ventricular wall motion in 137 patients and normal systolic motion in the remaining 43 patients. The difference between these two groups was a shorter mean time interval between the last attack of chest pain and angiography in the former group (p less than 0.001). Twenty-four patients had only abnormal diastolic wall motion. Twenty-one patients had a small increase in the creatine kinase level at the time of admission. Fifteen patients (nine before and six during early revascularization) had an anterior wall myocardial infarction in the hospital; these patients had a patent but severely narrowed LAD and a low incidence of collateral circulation to the LAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1989

Cost-benefit analysis of medical vs surgical treatment of symptomatic patients with accessory atrioventricular pathways.

Surgical treatment of patients with an accessory atrioventricular pathway leading to symptomatic arrhythmias provides effective control. However, surgical treatment is usually considered only when medical treatment fails. To assess the cost-benefit ratio of medical vs surgical treatment 77 patients treated with antiarrhythmic drugs were compared with 50 patients treated surgically. Cost was calculated by considering current costs for drugs, surgery and pacemakers, electrophysiological investigations, outpatient clinic controls, and costs of readmissions because of tachycardia. Mean cost per treated patient and mean cost per successfully treated patient (total cost divided by the number of patient not requiring readmission during follow-up) was respectively 4242 and 6949 US dollars after 56 months for the medically treated group and 10800 and 11250 US dollars for the surgically treated group. A projection of costs demonstrated that costs of medical treatment was the same as costs of surgical treatment after 12.5 years of treatment but a higher number of medically treated patients remain symptomatic. We conclude that surgical treatment of symptomatic patients with accessory pathways has a better cost-benefit ratio than medical treatment and should be considered earlier without waiting for failure for medical treatment.

Adolescent↗
PubMed1989

Use of a removable vena caval filter for prevention of recurrent embolism after emergency pulmonary embolectomy: a flexible approach.

Intraluminal vena caval filters, inserted via the transvenous approach, are used often in the prevention of recurrent pulmonary embolism. Until lately, such filters have been unremovable. In a recent case, however, we treated a patient who experienced acute massive pulmonary embolism after having undergone an emergency right hemicolectomy. He underwent a successful emergency pulmonary embolectomy with the help of cardio-pulmonary bypass; to prevent recurrent embolism, we inserted a removable intracaval filter through the right atriotomy with an introducer set. On the 7th postoperative day, the absence of significant residual thrombi was confirmed by means of phlebography, and the caval filter was removed percutaneously via the femoral approach. Although the value of routine use of the filter in this application has yet to be established, we feel that it warrants further investigation because it relieves the surgeon, during an emergency procedure, of the need to decide quickly whether or not to place a filter. The question becomes one of whether or not to remove the filter, and that decision can await the results of proper postoperative diagnostic studies.

Journal Article↗
PubMed1987

The management of preexcitation syndromes.

The introduction of new techniques such as epicardial mapping and programmed stimulation of the heart has made it possible to unravel most of the mysteries surrounding ventricular preexcitation. They helped us to understand the mechanisms of the arrhythmias that frequently are found in these patients and led to better-directed therapeutic interventions. The purpose of this article is to review this information and to indicate how it can be used in the treatment of the patient with preexcitation.

Anti-Arrhythmia Agents↗
PubMed1986

Endocardial catheter mapping: wire skeleton technique for representation of computed arrhythmogenic sites compared with intraoperative mapping.

Guiding surgical therapy of ventricular tachycardia by preoperative endocardial catheter mapping necessitates improvement of the accuracy of localization of the arrhythmogenic site. We therefore used a new mathematical cineradiographic method during catheter mapping to compute the position of left ventricular arrhythmogenic sites relative to three anatomic reference points: the centers of aortic and mitral valve ostia and the left ventricular apex. To enable the surgeon to identify the position of the computed sites, a wire skeleton (one for each patient) representing a single or multiple arrhythmogenic site(s) relative to the anatomic reference points was constructed. This wire skeleton was inserted into the left ventricular cavity during surgery. Side branches of the device indicated preoperatively localized arrhythmogenic sites. Results in eight consecutive patients were compared with those of intraoperative simultaneous mapping of 64 endocardial sites. Sixteen morphologically distinct monomorphic ventricular tachycardias were mapped by catheter and 15 by intraoperative mapping. In 12 ventricular tachycardias an identical morphology was recorded during both techniques. The distance between arrhythmogenic sites localized with both methods was 1 cm or less in 11 of these 12 ventricular tachycardias and 2 cm in one ventricular tachycardia. These results indicate that endocardial catheter mapping combined with wire skeleton representation of computed positions of arrhythmogenic sites is reliable for guiding surgical therapy of ventricular tachycardia and since some of the ventricular tachycardias were inducible only during either preoperative or intraoperative mapping, both techniques have an additive value. In addition, the wire skeleton proved convenient during surgery by identifying the arrhythmogenic sites.

Cardiac Catheterization↗
PubMed1984

Survival in 1041 patients with consecutive aorto-coronary bypass operations.

The first 1041 patients who underwent an isolated aorto-coronary bypass operation in the same institution since it opened in 1971, were followed for up to 10 years to determine their prognosis. The mean follow-up time was 3.5 years. The probability of survival at five years was 94 +/- 2% (95% confidence limits). This was similar to the survival of the general Dutch population matched for age and sex. Multivariate survival analysis with the proportional hazards model did reveal a relationship of the rate of death with sex and age at operation; however this was not significant. There was a trend to a higher death rate with more vascular involvement (rate ratio of 3 vessel-versus 1 vessel disease of 1.9, N.S.) and a significant association with a low ejection fraction (EF) (ratio EF less than or equal to 0.30 v. EF greater than or equal to 0.55 of 2.7. P less than 0.05). Though surgery seems to eradicate the poor longterm outlook for patients with more serious vascular disease, the adverse influence of decreased left ventricular function on survival is not changed.

Angina Pectoris↗