Biomedical subjects

R Frombach

Publications and source records attributed to R Frombach.

7 recordsLinked to original sources

PubMed1997

[Stent implantation in coronary arteries--current status].

Intracoronary stents have improved the safety and efficacy of transcatheter cardiovascular therapy. They can reverse acute vessel or graft closure during coronary intervention. Certain devices reduce the rate of restenosis and need for repeat interventional procedures compared with PTCA alone in selected patients. However caution is strongly recommended in generalising these findings to other situations than for which coronary stenting is considered. The rapid proliferation and application of this technique to very large groups of patients without supporting data should be reconsidered. Intermediate and longterm follow up date are not yet available.

Angioplasty, Balloon, Coronary↗

PubMed1993

Different vascular reactivity of human internal mammary and inferior epigastric arteries in vitro.

Vascular responses to endogenous agonists may determine patency rates of bypass graft conduits. The effect of constrictors (noradrenaline, phenylephrine, serotonin, histamine, angiotensin II) and dilators (acetylcholine, substance P, bradykinin, nitroglycerin) were compared in human internal mammary and inferior epigastric arteries in vitro. The latter vessel type has been recently advocated as an additional conduit for coronary artery bypass grafting. Whereas the alpha-adrenoceptor- (noradrenaline, phenylephrine) and serotonin receptor-mediated contractions were similar in both vessels, histamine-induced contractions were greatly enhanced in internal mammary arteries (maximal responses in percent of 80 mmol/L KCl, 131% +/- 15% versus 59% +/- 8%). Maximal contractions in response to angiotensin II were greater in inferior epigastric arteries (50% +/- 6% versus 25% +/- 5%). The endothelium-independent relaxations in response to nitroglycerin were identical in both vessels. In contrast, the endothelium-dependent relaxations in response to acetylcholine, substance P, and bradykinin were significantly greater in the inferior epigastric than in the internal mammary arteries (maximal relaxations expressed as percent of prostaglandin F2 alpha-induced precontraction: acetylcholine, 94% +/- 5% versus 77% +/- 5%; substance P, 85% +/- 4% versus 24% +/- 5%; bradykinin, 77% +/- 5% versus 26% +/- 3%). It is concluded that the inferior epigastric artery has a high endothelial capacity to release endothelium-derived relaxing factor. It appears that the inferior epigastric artery possesses credentials to be successfully used for coronary artery bypass grafting.

Abdominal Muscles↗

PubMed1993

Human parathyroid hormone dilates both pig coronary and human inferior epigastric arteries by a cyclic AMP-dependent pathway.

Human parathyroid hormone (hPTH (1-38)) induced concentration-dependent relaxations in prostaglandin F2 alpha-preconstricted pig coronary arteries in vitro. Removal of endothelial cells or pretreatment with nitro-L-arginine, a specific inhibitor of the endothelium-derived relaxing factor (EDRF) synthesis, impaired, although to a small extent, hPTH-induced relaxations. Human PTH-, but not bradykinin- or nitroglycerin-induced relaxations were potentiated in the presence of the cyclic AMP phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Human PTH also relaxed preconstricted human inferior epigastric arteries in vitro. In accordance to pig coronary arteries, this relaxation was potentiated in the presence of IBMX. However, the human internal thoracic (mammary) artery did not respond to hPTH (1-100 nM). Thus, acute vasodilatory effects of hPTH may not be present in all human arteries. The physiological significance of this phenomenon is not known. This relaxation, at least in pig arteries, is mediated to a small extent by the release of EDRF. In addition, this relaxation appears to be mainly mediated in both pig and human arteries by a smooth muscle cyclic AMP pathway.

Abdominal Muscles↗

PubMed1989

Coronary vasodilation with nitrocompounds--is there a maximum?

The maximal extent of the dilation of epicardial coronary arteries attainable with nitro-compounds was investigated in 12 patients with coronary artery disease. Before and 5, 10, 15, 19, 60 and 64 min after onset of a 4-min-intravenous infusion of 0.025 mg SIN-1/kg bodyweight coronary angiograms were performed in identical projection; simultaneously, the mean pulmonary wedge pressure (PWP) was measured. At 15 and 60 min, 0.8 mg nitroglycerin (NTG) were additionally administered as sublingual spray. Mean diameters of angiographically normal coronary segments were analyzed with the computer-assisted contour detection system CAAS; they increased by an average maximum of 29 +/- 5% prior to NTG (p less than 0.001). PWP decreased from 9.2 +/- 3.1 mmHg to an average minimum of 4.3 +/- 1.6 mmHg (p less than 0.01) prior to NTG. Neither of these SIN-1-effects was significantly augmented by additional NTG: at 19 min coronary dilation amounted to 28 +/- 7% (p less than 0.001), PWP to 3.9 +/- 1.0 mmHg (p less than 0.01). At 60 min coronary dilation still amounted to 24 +/- 8% (p less than 0.001), PWP to 6.2 +/- 2.5 mmHg (p less than 0.05). By the second administration of NTG the maximal effects attained before could be reproduced: coronary dilation 28 +/- 8% (p less than 0.001), PWP 4.6 +/- 2.2 mmHg (p less than 0.01). Thus, the dilation reserve of epicardial coronary arteries for nitrocompounds is approximately 30% on average. These results suggest the possibility of a reproducible maximal activation of the enzyme guanylate cyclase which seems to be the mediator of the nitro-compound-induced vasodilation.

Administration, Sublingual↗

PubMed1989

[The status of echocardiography within the scope of routine cardiologic diagnosis].

In particular since the introduction of the two-dimensional approach, echocardiography as a non-invasive and easily repeatable bedside-technique without side-effects plays a central role within the diagnostic tools of cardiology. The following applications of cardiac ultrasound are commonly accepted and sufficiently validated: Assessment of the size of cardiac chambers including qualitative and quantitative evaluation of left ventricular function, detection of pericardial effusion, diagnosis of intra- and extracardiac tumors and thrombi, analysis of complex congenital diseases. Without the use of Doppler, valvular regurgitations can only be suspected by indirect parameters; in contrast, stenotic lesions as well as a variety of other valve abnormalities (calcifications/partial rupture/prolapse/vegetations) can be diagnosed with a high accuracy. Transesophageal echocardiography guarantees not only an optimal imaging quality in virtually all patients, in addition, the technique allows the routine visualization of the thoracic descending aorta and the left atrial appendage which is of importance for the diagnosis of aortic dissection and isolated left atrial appendage thrombi. Transesophageal echocardiography is also superior to the conventional precordial approach concerning the assessment of prosthetic valve malfunction (in particular in mitral position) and endocarditis-associated abscesses. Today, the echocardiographic visualization of coronary arteries is without clinical relevance.

Aortic Dissection↗

PubMed1989

[Continuous pH registration in the coronary sinus in vivo in ischemic and normoxic lactic acidosis using an ion sensitive field effect transistor catheter].

A new catheter with an Ion Sensitive Field Effect Transistor (ISFET) for continuous measurements of blood pH in vivo was employed. In canine heart preparations (n = 15), two catheters were positioned in the coronary sinus and in the abdominal aorta, respectively. A close agreement between pH-measurements with the pH-ISFET-sensor and the corresponding pH-determinations on blood samples by conventional means (r = 0.97; pH-range 7.15-7.50) was found. The ISFET-sensor revealed a sensitivity of 50-55 mV/pH, a long-term drift rate of 1-2 mV/h, as well as a response time shorter than 100 ms. The ISFET-sensor was sensitive for the detection of respiratory and metabolic acidosis and alkalosis (hypo-, hyperventilation, myocardial ischemia, intracoronary infusion of 0.3-M lactic acid). There was a close correlation between the changes of coronary venous pH and lactate concentrations during myocardial ischemia (r = 0.83; n = 9). During ischemic acidosis there was a drastic reduction of left ventricular dp/dtmax, whereas contractility changes during normoxic lactacidosis were moderate. The pH-decrease (pH = 7.1) was identical in both interventions. The observed data suggest that the newly developed ISFET-pH-catheter is working precisely and enables respiratory and metabolic control of the whole organism as well as of individual organs.

Acid-Base Equilibrium↗

PubMed1987

Ascorbic acid: a nonradioactive extracellular space marker in canine heart.

The distribution pattern of ascorbic acid and L-[14C]ascorbic acid in myocardial tissue was compared with those of the classical radioactive extracellular space markers [3H]-inulin, [3H]sucrose, and Na82Br. A new polarographic technique was developed for analogue registration of ascorbic acid concentration in coronary venous blood. The kinetic data of the markers were studied in an open-chest canine heart preparation (n = 17 dogs) during a constant tracer infusion of up to 9 min. Distribution volumes were calculated based on the mean transit time method of Zierler (K. L. Zierler, Circ. Res. 10:393-407, 1962). The distribution volume of ascorbic acid (23.6 ml/100 g wet wt) as well as of L-[14C]ascorbic acid (24.5 ml/100 g wet wt) in myocardial tissue agreed closely with those of [3H]inulin (18.6 ml/100 g wet wt) and [3H]sucrose (22.0 ml/100 g wet wt), as well as 82Br- (27.3 ml/100 g wet wt). The obtained kinetic data confirmed that ascorbic acid exhibits the physicochemical properties of an extracellular space marker, though this compound was shown to leak slowly into myocardial cells. Favorable attributes of this indicator are its low molecular weight, high diffusibility in interstitial fluid, low binding affinity to macromolecules, and high transcapillary (1.8 X 10(-5) cm/s) as well as low transplasmalemmal penetration rate (3.7 X 10(-8) cm/s). Therefore, this nonradioactive marker can be applied in a safe and simple fashion, and without untoward side effects in experimental animals as well as in patients.

Animals↗