Biomedical subjects

D N Chrysos

Publications and source records attributed to D N Chrysos.

4 recordsLinked to original sources

PubMed1988

Effect of acute hypertension on the cardiac rhythm. Experimental observations.

An acute increase in blood pressure (BP) may be associated with the genesis of ventricular ectopy. Fourteen anesthetized dogs were examined to find out whether the critical pressure that causes an arrhythmia may be an index of the tendency of the myocardium to generate ectopic rhythms. An acute change in BP was produced 321 times using an arterial pressure reservoir or aortic obstruction or a metaraminol infusion or, inversely, arterial bleeding. Each time the BP was increased, cardiac arrhythmias appeared and each time the BP was decreased the cardiac arrhythmias disappeared. The most common type of arrhythmia was ventricular ectopy (123/167 acute BP increases), usually in a form of bigeminy. The next most common rhythm disturbance was atrioventricular block (32/167 acute BP increases), especially when a constant rate was achieved by atrial pacing. The BP above which an arrhythmia appeared varied greatly among different animals (189.0 +/- 55.1 mmHg, means +/- SD). It was significantly (p less than 0.01) reduced (-29.0 +/- 17.1 mmHg) following coronary ligation and significantly (p less than 0.05) raised (+/- 41.6 +/- 38.7 mmHg) following lidocaine administration. The incidence of ventricular ectopy on increasing the BP was significantly higher at low heart rates in ten experiments, lower in two and not significantly different in 14. The incidence of premature ventricular complexes, the degree of atrioventricular block and the PR interval in first-degree atrioventricular block, whenever these rhythm disorders appeared, were a function of the BP level. It is concluded that an acute increase in BP may cause rhythm disturbances, usually in the form of ventricular ectopy and/or atrioventricular block.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1987

An extravascular hydraulic system to control blood pressure by a feedback regulation of the venous return.

Since increases in blood pressure may be effectively controlled by hydraulic feedback by reducing the venous return through the inferior vena cava in proportion to the blood pressure this principle was applied using a totally implantable extravascular system consisting of a periaortic blood pressure sensor and a pericaval cuff around the inferior vena cava. The two cuffs were supported externally by hard skeletons, filled with water, and connected directly to each other. The two devices were tested separately and together in 10 anaesthetised mongrel dogs with normal and high blood pressure induced by a metaraminol infusion. With the periaortic sensor an increase in blood pressure of 100 mmHg caused a mean(SD) isotonic volume displacement of 0.41(0.11) ml, and an increase in the pericaval balloon energy content of 100 ml.mmHg-1 caused a fall in blood pressure of 37.8(18.3)%. The whole system prevented an excessive rise in blood pressure when metaraminol was infused, with a feedback gain of about 2.8. It is concluded that blood pressure can be maintained at acceptable levels despite strong hypertensive stimuli, by this system, without additional treatment with drugs or an external energy source. The system is totally implantable and is applied extravascularly so that no anticoagulation is needed.

Animals↗

PubMed1985

Pressure volume parameters for optimal function of an intraaortic balloon without a pump.

An air filled intraaortic balloon connected to an extravascular air chamber (compression chamber system-CCS) was used in 10 anesthetized dogs to increase its stroke volume (SV). Highest SV increases (up to over 200%) were observed at low SV states, with a high CCS volume and with high increases of the systolic pressure. The CCS pressure--systolic pressure relationship was a sigmoid-like curve. In conclusion, highest SV's may be achieved at low SV states, using CCS volumes about 400 ml and the highest CCS pressure that may cause a linear aortic pressure increase.

Animals↗

PubMed1983

Intra-aortic balloon assistance without a pump.

An intra-aortic compression chamber system (CCS) was utilized in 19 anaesthetized dogs and in seven patients. The CCS consisted of an intra-aortic balloon in the thoracic aorta, an external rigid wall air chamber, and a catheter connecting the other two parts. The CCS, inflated for 2-3 min to a pressure between the systolic and diastolic arterial pressures, caused changes in the following measurements (compared with those immediately before inflation, and after deflation to atmospheric pressure): a significant (P less than 0.001) increase in cardiac output (7.8 +/- 18.8% means S.D.), aortic compliance (12.8 +/- 29.6%), aortic resistance (20.1 +/- 32.7%), cardiac power (or minute work, + 36.7 +/- 44.6%), coronary sinus outflow (+ 23.6 +/- 43.6%) and aortic backflow (+ 28.0 +/- 36.4%); the left ventricular end-diastolic pressure did not change significantly. During a 5-90 min utilization in seven patients with cardiogenic shock, the cardiac output was increased by 4.1 +/- 42.4% (lower than when intra-aortic balloon pumping was applied). It is concluded that the simple device described may be useful in clinical cardiogenic shock, especially when an intra-aortic balloon pump is not available or a portable device is desirable.

Animals↗