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Biomedical subjects

Tomas Klima

Publications and source records attributed to Tomas Klima.

8 recordsLinked to original sources
PubMed2003

Acquired commissural fusion of aortic valves in patients with left ventricular assist devices.

BACKGROUND: Left ventricular assist devices (LVADs) currently are used as bridges for patients who deteriorate clinically while awaiting cardiac transplantation. At the time of transplantation or subsequent death, we can assess the effect of long-term device implantation on cardiac structural changes. We have noted, in our years of experience, that aortic valve commissures may fuse in patients supported by LVADs. These observations may be important in the use of these pumps as long-term destination therapy. METHODS: We examined 33 hearts (both explants and autopsy specimens) from patients supported either with vented-electric (VE) HeartMates (n = 21) or with implantable pneumatic HeartMates (n = 12). We noted commissures involved, fusion length (mm), duration of LVAD support, and type of LVAD. As controls, we examined 49 explanted hearts from patients with heart failure who were not supported by LVADs. RESULTS: We found commissural fusion in 17 of the 33 hearts. Of those 17 hearts, 4 (23.5%) had 2 commissural fusions, and 13 (76.5%) had only 1 fusion. Fusion length ranged from 5 mm to 17 mm (mean, 9.9 mm). The lesion was more common in patients fitted with VE HeartMates (p < 0.0002). We found small amounts of commissural fusion in 8 of the 49 control hearts. CONCLUSIONS: Acquired commissural fusion is common in patients supported by LVADs, particularly the VE HeartMate. The lesion also occurs occasionally in failing hearts of patients not supported by LVADs. The significance of the lesion in patients who require long-term LVAD support either as a bridge to transplantation or as destination therapy is unclear.

Aortic Valve↗
PubMed2002

Near-infrared spectroscopic characterization of human advanced atherosclerotic plaques.

UNLABELLED: OBJECTIVES; Living human carotid atherosclerotic plaques were examined in vitro by near-infrared (NIR) spectroscopy to determine the spectral features of plaque vulnerability. BACKGROUND: Plaque disruption, a major cause of heart attacks and strokes, cannot generally be predicted, but is thought to depend mainly on plaque composition. Near-infrared spectroscopy has been used to detect components in tissues noninvasively. METHODS: Using an NIR spectrometer fitted with a fiberoptic probe, living human carotid atherosclerotic plaques (from 25 patients) were examined ex vivo for plaque vulnerability. The plaques were cut into smaller sections according to their gross pathologic features, and NIR measurements were done at 20 degrees C, usually within 10 min. RESULTS: According to the American Heart Association's recommended classification scheme, the lesions were classified into three groups: the first group comprised of vulnerable type V/VI lesions; the second group, stable type I/II lesions; and the third (intermediate) group, mainly type III/IV lesions. Cluster analysis of the specimens' NIR spectra identified three major composition groups in each of the three NIR spectral regions: 2,200 to 2,330 nm, 1,620 to 1,820 nm and 1,130 to 1,260 nm. Calculation of the lipid/protein ratios in each group at two NIR regions (2,200 to 2,330 nm) revealed ratios of 1.49 +/- 1.20, 2.12 +/- 1.00 and 3.37 +/- 0.88 for type I/II, type III/IV and advanced type V/VI lesions, respectively (p < 0.03). At 1,620 to 1,820 nm, the respective ratios for these histologic groups were 0.57 +/- 0.21, 1.54 +/- 0.46 and 2.40 +/- 0.44 (p < 0.00003). CONCLUSIONS: The good ex vivo discrimination of histologically vulnerable and stable plaques in this study suggests that NIR spectroscopy has the potential to identify vulnerable atherosclerotic plaques in vivo.

Animals↗
PubMed1980

Recurrent myocardial infarction in a patient with Prinzmetal's angina and normal coronary arteries.

A 55-year-old man was referred for the evaluation of frequent chest pain and syncope. While in the hospital, he experienced severe chest pain accompanied by transient ST segment elevation and a slight elevation of cardiac enzyme levels. Multiple coronary arteriograms were recorded at various times during an interval of 2 months. On one occasion, the results were normal; on another occasion, they showed total occlusion of the left anterior descending, diagonal, and circumflex coronary arteries. The occlusion was completely relieved with sublingual nitroglycerin. Because the patient's clinical condition deteriorated rapidly, double aortocoronary saphenous vein bypass was performed to the left anterior descending and circumflex coronary arteries. During the induction of anesthesia, ventricular fibrillation occurred, and the patient died from refractory recurrent fibrillation 4 hours after surgery. Postmortem examination revealed normal coronary arteries, patent vein grafts, and multiple focal areas of recent and old myocardial fibrosis. Thus, it appears that coronary spasm, in the presence of otherwise normal coronary arteries, can produce myocardial infarction with necrosis, and that medical management may provide a more successful method of treating such patients.

Journal Article↗
PubMed1979

ATHEROSCLEROSIS OF AORTOCORONARY ARTERY SAPHENOUS VEIN BYPASS GRAFTS.

Among a series of 109 patients who underwent aortocoronary artery bypass reoperation and received a total of 168 grafts, atherosclerosis was found in 29 saphenous vein grafts. Specimens were obtained at reoperation in 25 patients and at postmortem examination in four. Plaques were found from 3 months to 6 years after operation. The plaques often were combined with old or recent mural thrombi, intimal fibroses, or thickened intima associated with intramural hematomas. Clinical findings did not correlate with risk factors such as hypercholesterolemia, hypertension, or diabetes mellitus. In a well-functioning graft with adequate flow, cellular proliferation generally reflects an adjustment of the venous wall to a higher pressure. Such a vessel retains elastic properties of pulsating structures. In the specimens studied, intimal fibrosis associated with plaques was always poorly cellular, causing the grafts to become rigid. This resulted in irregular flow and, in some patients, dissection. The possible pathogenesis of atheromatosis in vein grafts may include the usual mechanisms of atherogenesis and atheromatous transformation of thrombi. It appears that hemodynamically significant stenosis of vein grafts caused by atherosclerosis is an infrequent complication.

Journal Article↗
PubMed1978

MACROSCOPIC, MICROSCOPIC, AND MECHANICAL ANALYSES OF PROTOTYPE DOUBLE VELOUR VASCULAR GRAFTS.

In-vivo and ex-vivo evaluations of two prototype double velour tube grafts have been conducted. The experimental grafts were fabricated from terry cloth derivatives of the Dacron polyester material that is used in the construction of presently available Microvel(R) Double Velour and Cooley Double Velour Guideline(R) grafts.(*) The use of terry cloth derivatives in the experimental grafts provides a velour pile that is more uniform in height and density than current clinical grafts. The hypothesis examined by these studies was whether the utilization of terry cloth derivatives provides a more perfect capsular and luminal surface for fibrous tissue attachment and ingrowth, thereby enhancing neointimal formation at the blood contacting surface. Using standard techniques, prototype grafts were implanted in the abdominal aortas of dogs for test periods of 1 to 6 months. All grafts remained patent throughout the healing period. At explantation, the macroscopic and microscopic properties of the grafts were examined and characterized. Neointimal analysis demonstrated that the lighter denier, higher porosity prototype consistently produced more homogeneous blood-contacting surfaces with smoother contours and more complete endothelialization than the heavier denier, lower porosity prototype. From these analyses, we can conclude that both prototype grafts possess the basic properties of useful arterial prostheses. They are not prone to early thrombosis, and exhibit rapid healing properties. This study indicates that the use of terry cloth derivatives provides a more uniform, less random velour pile and that arterial grafts constructed from such materials produce more uniform and biologically stable neointimas.

Journal Article↗
PubMed1977

ANGIOSARCOMA OF THE HEART.

A case of primary angiosarcoma arising in the right atrium is described. The clinical, pathological, therapeutic and prognostic features are discussed. A review of the literature reveals 52 cases to date, including the present case.

Journal Article↗
PubMed1975

SEGMENTAL AORTITIS AND AORTIC INCOMPETENCE.

An unusual case of a middle-aged male with segmental aortitis and aortic incompetence is described. To our knowledge, only 13 cases have been previously described in the literature, but only two have had anatomopathological confirmation. Aortic incompetence is a rare manifestation of segmental aortitis. Although intrinsic abnormalities of the aortic valve have been proposed, the finding of a normal aortic valve at postmortem examination in 2 of the 3 cases in which the aortic valve was examined, supports the premise that the incompetence is probably secondary to disproportionate dilatation of the aortic root.

Journal Article↗