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At least 1,333 records · Page 74Linked to original sources
PubMed1995

Nitrate versus rest myocardial scintigraphy with technetium 99m-sestamibi: relationship of tracer uptake to regional left ventricular function and its significance in the detection of viable hibernating myocardium.

Rest technetium 99m-sestamibi uptake may underestimate myocardial viability in asynergic territories. Because nitrate administration was reported to improve thallium 201 uptake in perfusion defects, this study aimed to test the influence of nitrates on 99mTc-sestamibi uptake and on the tracer capability to recognize viable tissue in asynergic segments. In 23 patients with prior infarction and left ventricular dysfunction, regional wall motion was assessed by echocardiography before and after revascularization (13 segments/patient). Group 1 included 97 normokinetic; group 2, 97 hypokinetic; and group 3, 105 akynetic or dyskinetic segments; group 3 was divided into group 3A (72 segments unchanged after revascularization) and group 3B (33 segments with functional recovery). 99mTc-sestamibi uptake was graded using a scoring scheme in the same 13 segments both at rest and, on a separate day, injecting the tracer during isosorbide dinitrate infusion (ISDN). At rest, the mean 99mTc-sestamibi uptake decreased significantly from group 1 through group 3. With ISDN, the mean 99mTc-sestamibi uptake increased in all groups compared with rest, but the increase was significant only in groups 2 and 3, and within the latter, only in group 3B. Thus, with ISDN group 3B was no longer different from group 2. Only 6% of group 3A segments showed an improved uptake with ISDN, versus 33% of group 3B (P < .00005). At rest only 14 of 33 segments of group 3B showed a normal or slightly reduced uptake, whereas these were 25 of 33 with ISDN (P < .02). In conclusion, the acute administration of ISDN increases the uptake of 99mTc-sestamibi mainly in those asynergic territories that show postrevascularization functional recovery. Therefore, ISDN 99mTc-sestamibi imaging might improve the tracer capability to detect viable hibernating myocardium.

Angioplasty, Balloon, Coronary↗
PubMed1995

Does interstitial adenosine mediate acute hibernation of guinea pig myocardium?

OBJECTIVE: The aim was to test the role of interstitial adenosine in protective downregulation of myocardial energy demand during myocardial hibernation. METHODS: Isolated working guinea pig hearts, perfused with glucose fortified Krebs-Henseleit, were subjected to 60 min global low flow ischaemia followed by 30 min reperfusion. Left ventricular performance was assessed from heart rate-developed pressure product and pressure-volume work. Cytosolic energy level was indexed by creatine phosphate and ATP phosphorylation potentials measured in snap frozen myocardium. Lactate and purine nucleosides (adenosine, inosine) were measured in venous effluent. RESULTS: When coronary flow was lowered by 80% for 60 min, heart rate-pressure product and pressure-volume work fell 87% and 75%, respectively, and stabilised at these low levels, but fully recovered when flow was restored. Myocardial ATP phosphorylation potential fell by 67% during the first 10 min of ischaemia, but subsequently recovered to preischaemic levels despite continuing ischaemia, indicating down-regulation of myocardial energy demand. Lactate release increased about 10-fold during ischaemia and remained increased until reperfusion. Purine nucleoside release varied reciprocally with phosphorylation potential, peaking at 10 min of ischaemia, then gradually returning to the preischaemic level during the subsequent 50 min of ischaemia. The ecto 5'-nucleotidase inhibitor alpha,beta-methylene adenosine 5'-diphosphonate (50 microM) decreased ischaemic purine nucleoside release by 41%, but did not attenuate postischaemic contractile recovery. The unspecific adenosine receptor antagonist 8-p-sulphophenyl theophylline (8-SPT, 20 microM) doubled ischaemic lactate release and lowered coronary venous purine nucleoside release by 21%. 8-SPT increased phosphorylation potential at 10 min ischaemia relative to untreated hearts, but blunted the subsequent rebound of phosphorylation potential. 8-SPT treatment during ischaemia resulted in a significantly higher cytosolic phosphorylation potential at 30 min of reperfusion, but did not affect postischaemic contractile function. CONCLUSIONS: We conclude that activation of adenosine receptors results in recovery of cytosolic energy level of moderately ischaemic working myocardium, but this energetic recovery is not solely responsible for postischaemic contractile recovery.

5'-Nucleotidase↗
PubMed1993

[Assessment of myocardial perfusion abnormality and hibernating myocardium by gated blood pool and exercise-stress thallium tomographies after successful coronary angioplasty].

Cardiac function and myocardial perfusion were assessed by exercise-stress thallium SPECT and resting gated blood pool SPECT techniques before and after 47 successful coronary angioplasties. Thallium perfusion was analyzed visually and quantitatively in stress and resting studies. Left ventricular ejection fraction (LVEF) and peak filling rate (PFR) were calculated and regional wall motion was scored by amplitude and phase images in radionuclide planar and tomographic imagings. The thallium redistribution in delayed or resting SPECTs was more sensitive (87%) for detecting myocardial ischemia compared to symptoms (36%) and ECG changes (60%). An exercise capacity, LVEF, PFR, and the scores of perfusion and regional wall motion were improved significantly after coronary angioplasty. Stress thallium and gated blood pool SPECTs showed the improvements of myocardial perfusion in 159 (79%) of 201 segments and regional wall motion in 47 (51%) of 92 segments, respectively. These results suggest that the combined use of stress thallium SPECT, gated blood pool planar and SPECT techniques can contribute not only to the assessment of the efficacy of coronary angioplasty but also to detecting the mismatching of myocardial perfusion and contraction ("myocardial hibernation") in infarct-related myocardial lesions.

Angina Pectoris↗
PubMed1995

Metabolic aspects of hibernating myocardium.

Myocardial hibernation describes the clinical entity of a dysfunctional region of myocardium with reduced flow that shows improvement in function after flow is restored. It is postulated that despite the reduced flow, metabolic activity is sufficient to prevent tissue necrosis. Experimental work in animals supports this. A moderate reduction in flow to a region of the left ventricle in pigs initially results in the typical metabolic picture of ischemia: ATP and PCr fall and anaerobic metabolism is present. However, over the next hour, a hypometabolic response occurs that eliminates almost all metabolic findings of ischemia despite ongoing flow reductions. This appears to be an actively and tightly regulated response. The reduction in systolic function is an important part of the hypometabolic state, but cannot fully account for the downregulation of energy use.

Adenosine Triphosphate↗
PubMedDate not supplied

Myocardial stunning and hibernation.

Hibernating myocardium is a potentially reversible form of left ventricular (LV) dysfunction the treatment of which improves function and prognosis. The identification of viable myocardium is critical in deciding which patients undergo revascularisation. Stunning is a clinically relevant phenomenon and it has been suggested that repeated episodes of stunning may cause chronic LV dysfunction. If this is the case then pharmacological agents which prevent stunning could represent a potential treatment of chronic LV dysfunction in patients with CAD.

Animals↗
PubMed1997

[Hibernation and stunning: conditions with reversible left ventricular dysfunction].

Hibernation and stunning are important causes of reversible left ventricular dysfunction in patients with ischaemic heart disease. A case is presented where these conditions precipitated referral for cardiac allograft transplantation, and where left ventricular function was found to be markedly improved after two years in the absence of transplantation.

Adult↗
PubMed1997

[Myocardial reperfusion: salvation or danger for the heart muscle? Stunning, hibernation and preconditioning: the states of endogenous cardiac protection against ischemia].

During most of our decade myocardial ischemia was regarded as an all-or-nothing phenomenon, either resulting in myocardial necrosis in case of severe and prolonged ischemia, or in negligible changes when ischemia was transient and mild. This view has been challenged in the wake of new discoveries during the last 15 years which indicate that depressed myocardial contractility with preserved viability may exist during or following ischemic insults. The clinical and pathophysiologic characteristics of these ischemic myocardial syndromes--stunning, hibernation and preconditioning--are discussed in the present overview.

Humans↗
PubMed1998

Medium-term results of coronary artery bypass surgery in patients with severe left ventricular dysfunction and preoperatively documented hibernating myocardium.

In patients with multivessel coronary artery disease (CAD), severe left ventricular dysfunction (LVD) and hibernating myocardium (HM) demonstrated on preoperative assessment, coronary artery bypass grafting (CABG) surgery can be performed safely with low operative morbidity and mortality rates. Surgical revascularization of reversibly dysfunctional myocardium improves significantly both patient's clinical status and left ventricular ejection fraction (LVEF). Diagnosis of HM prior to CABG surgery seems to be crucial because it does not leave the patient with multivessel CAD and LVD a candidate only for heart transplantation (HTX). In the presence of HM, more aggressive surgical approach could be recommended to salvage chronically jeopardized but viable myocardium using not only routine CABG procedures in extracorporeal circulation (ECC) but also alternative approach of coronary endarterectomy (EAE) or minimally invasive direct coronary artery bypass grafting (MIDCAB) procedures on beating heart, without any adverse impact on operative mortality.

Coronary Artery Bypass↗