Postoperative evaluation of myocardial blood flow in aorta-to-coronary artery vein bypass grafts using the xenon-residue detection technic

Effects of urotensin II on intracellular pH regulation in cultured human internal mammary artery smooth muscle cells

The Na(+)-H(+) exchanger (NHE) and the Na(+)-HCO3(-) co-transporter (NBC) have been confirmed as two major active acid extruders in many mammalian cells. Whether the NHE and NBC functional co-exist in human internal mammary artery smooth muscle cells (HIMASMCs) remains unclear. The aims of the present study were to investigate the acid-extruding mechanisms and to explore the effects of urotensin-II (U-II), a powerful vasoconstrictor, on pHi regulators in HIMASMCs. We investigated the changes of pHi by BCECF-fluorescence in HIMASMCs. We found that (a) two Na(+)-dependent acid extruders, i.e. NHE and NBC, functionally co-exist; (b) U-II (3-100 nM) induced a concentration-dependent intracellular acidosis; and (c) U-II (3-100 nM) caused a concentration-dependent increase on NHE activity, while decrease on NBC activity. In summary, we demonstrate for the first time that two acid-extruders, NHE and NBC, functionally co-exist in HIMASMCs. Moreover, U-II induces a concentration-dependent intracellular acidosis through the balanced effect of its effect on increasing NHE activity and decreasing NBC activity.

Cardiac nuclear medicine, present status, future hopes as seen from the view of a cardiologist

The present techniques of nuclear medicine that are used in cardiology are critically evaluated. They are used mainly for the assessment of coronary circulation (measurement of regional flow and perfusion), on the determination of left ventricular muscle function (radionuclear ventriculography) and on the study of cardiac metabolism. The last-mentioned technique is unique insofar as (except for magnetic resonance imaging) there is no other method available to analyse myocardial metabolism noninvasively in living man. Of immense practical importance is the diagnosis and quantitation of the abnormal coronary flow and perfusion, as coronary artery disease is one of the major diseases of the Western world. Finally, the value of nuclear imaging techniques is compared with that of other nonnuclear methods. In present-day medicine, with its increasingly high costs, the value of nuclear techniques must be assessed very carefully.

Extensive myocardial blood flow distribution through individual coronary artery bypass grafts

The regional myocardial perfusion distribution of coronary artery bypass grafts were studied in 61 patients who received 162 grafts. Selective intragraft instillations of radioactive-labeled macroaggregated albumin particles were used to study perfusion. The extent of individual graft perfusion was assessed in 100 patent grafts. Regional myocardial blood flow distribution was similar to the blood flow distribution of the native vessel receiving the graft in 64 of 100 grafts and less than that expected of the native vessel in 12 grafts. However, 24 grafts demonstrated a blood flow distribution pattern which extended beyond the normal distribution expected of the native vessel receiving the graft. This extensive perfusion could be attributed to collateral vessels or retrograde flow. A high incidence of both graft and native vessel occlusion was found in areas receiving blood from these distant grafts with extensive distributions (16/24), and left ventricular wall motion was preserved or significantly improved postoperatively in 28/31 segments in such areas. When comparing angiographic and scintigraphic methods of evaluating myocardial perfusion, the angiogram underestimated the full extent of graft blood flow distribution in 13 of 24 instances (54 percent).

Value of coronary bypass surgery. Controversies in cardiology: Part I

The value of coronary bypass surgery has been studied carefully during the last decade. Four methods, none perfect, have been used to compare the results of such surgery with the results of medical therapy. New data are likely to be merely supportive rather than the outcome of a definitive study with a new and a acceptable experimental design. It is therefore time to analyze the available data in light of the treacherousness of the disease and to determine if a clear trend is evident. There appears to be sufficient evidence to state that properly performed coronary bypass surgery will increase coronary blood flow and relieve angina pectoris in 90 percent of patients; total relief of angina can be expected in 60 percent and partial relief in 30 percent. Compared with modern medical therapy, properly performed coronary bypass surgery appears to prolong the life of patients who have obstruction of the left main coronary artery or triple or double vessel disease. There is not adequate evidence to state that the procedure will prolong the life of patients with single vessel obstruction. However, patients with single vessel obstruction and unacceptable angina pectoris should be considered for bypass surgery (especially patients with obstruction of the left anterior descending coronary artery). In practice, at Emory University Hospital, Atlanta, bypass surgery is recommended for young people with few symptoms if compelling obstructing lesions are present and in older patients only if their symptoms require it. Medical therapy is given before and after bypass surgery. When bypass surgery is performed in an excellent fashion (operative risk 1 percent) a great deal of "controversy" about this problem vanishes.

Definition of myocardial perfusion by continuous infusion of krypton-81m

Krypton-81m, a radionuclide emitting a 190 kev gamma ray, has a half-life of 13 seconds. It is a radioisotope of an inert water-soluble noble gas and is produced at a constant rate by spontaneous decay of rubidium-81 in an 81Rb-81mKr generator-delivery system. Delivery is through a minibore Teflon catheter that can be threaded through a standard no. 7 or 8F angiographic catheter. The generator is eluted by 5 percent dextrose-in-water, delivered by infusion pump at 1.5 ml/min, and the eluate is infused intraarterially directly into any organ. Delivery and decay reach equilibrium within 2 minutes, producing a heterogeneous distribution that is proportional to the perfusibility of the tissue concerned and the time required to reach it. The ultrashort halflife of the radionuclide rapidly eliminates activity when delivery ceases; thus, experiments can be sequentially repeated at brief intervals. The radiation hazard for easily imaged doses is negligible. Preliminary studies in open chest dogs were visualized by scintillation camera, stored on digital data disk, processed, and displayed in dual channel, dual color mode on a video system. Images of myocardial perfusion defined relative levels of perfusion, collateral circulation between coronary arterial branches, equilibrium time of diffusible perfusion of the myocardium, focal defects in induced occlusion, collateral circulation to occlusion, and reactive hyperemia after release of induced coronary occlusion. The system and technique appear applicable to human subjects.

Evaluation of perfusion with the 81Rb-81mKr generator

The development of the 81Rb-81mKr generator-delivery system has made available an ultrashort (13-sec) half-life radionuclide for continuous, constant-rate delivery as a gas, or as an isotonic, nonionic solution in 5% dextrose and water. This system has been evaluated and applied to the scintigraphic imaging of various organs and anatomic regions by intravenous and intraarterial infusion and by inhalation and deglutition. This diffusible, noble gas is inert chemically and biologically. When the gas is administered intraarterially, the volume of tissue being perfused may be defined with the scintillation camera. The 13-sec half-life is of a similar magnitude to the rate of capillary exchange, producing a heterogeneous image with steady-state administration in which the intensity of detectable radioactivity is proprotional to the time of diffusion into the tissue. This system appears capable of defining the rate of capillary exchange and the moment-to-moment changes brought about by vasoactive stimuli in specific organs.