Hemodialysis-induced cardiac dysfunction is associated with an acute reduction in global and segmental myocardial blood flow.

Background And Objectives: Hemodialysis is associated with hemodynamic instability, acute cardiac ischemia, and the development of regional wall motion abnormalities (RWMAs). This study used serial intradialytic H(2)(15)O positron emission tomography scanning to confirm that the development of dialysis-induced RWMAs was associated with reduction in myocardial blood flow (MBF).

Design, Setting, Participants, & Measurements: Four prevalent hemodialysis patients without angiographically significant coronary artery disease had measurements of MBF during standard hemodialysis and biofeedback dialysis.

Evaluation of the microcirculation in hypertension and cardiovascular disease.

The ability to investigate the microvascular structure and function is important in improving our understanding of pathophysiological processes in hypertension and related cardiovascular disease. A range of techniques are available or emerging for investigating different aspects of the microcirculation in animals and humans. Techniques such as experimental intravital microscopy and clinical intravital microscopy (e.

Pre- and post-synaptic sympathetic function in human hibernating myocardium.

Purpose: Impaired pre-synaptic noradrenaline uptake-1 mechanism has been reported in a swine model of hibernating myocardium (HM). To ascertain whether adrenergic neuroeffector abnormalities are present in human HM, we combined functional measurements in vivo using cardiovascular magnetic resonance (CMR) and positron emission tomography (PET) to assess pre- and post-synaptic sympathetic function.

Methods: Twelve patients with coronary artery disease and chronic left ventricular (LV) dysfunction underwent CMR at baseline and 6 months after bypass for assessment of regional and global LV function and identification of segments with reversible dysfunction.

Systemic nitric oxide synthase inhibition improves coronary flow reserve to adenosine in patients with significant stenoses.

We studied the impact of systemic infusion of the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA) on coronary flow reserve (CFR) in patients with coronary artery disease (CAD). We have previously demonstrated that CFR to adenosine was significantly increased after systemic infusion of L-NMMA in normal volunteers but not in recently transplanted denervated hearts. At baseline, myocardial blood flow (MBF; ml x min(-1) x g(-1)) was measured at rest and during intravenous administration of adenosine (140 microg x kg(-1) x min(-1)) in 10 controls (47 +/- 5 yr) and 10 CAD patients (58 +/- 8 yr; P < 0.

Myocardial pre-synaptic sympathetic function correlates with glucose uptake in the failing human heart.

Purpose: We have previously shown that the myocardium of patients with heart failure (HF) is insulin resistant. Chronic beta-adrenergic stimulation has been implicated in insulin resistance in cultured cardiomyocytes in vitro, where sustained noradrenaline stimulation inhibited insulin-modulated glucose uptake. As the failing heart is characterized by increased sympathetic drive, we hypothesized that there is a correlation between pre-synaptic sympathetic function and insulin sensitivity in the myocardium of patients with HF.

Myocardial glucose transport and utilization in patients with type 2 diabetes mellitus, left ventricular dysfunction, and coronary artery disease.

Objectives: This research was designed to assess the effect of type 2 diabetes mellitus (T2DM) on myocardial glucose utilization in patients with heart failure secondary to coronary artery disease.

Background: Patients with T2DM and coronary artery disease have an increased morbidity and mortality compared with patients with coronary artery disease without diabetes that may relate to a reduction in the ability of the myocardium to utilize glucose.

Methods: Myocardial blood flow and glucose utilization were assessed during a hyperinsulinemic clamp by 18F-flurodeoxyglucose and positron emission tomography in 54 patients (19 with T2DM) with multivessel coronary artery disease and heart failure.

Effects of long-term oral dipyridamole treatment on coronary microcirculatory function in patients with chronic stable angina: A substudy of the persantine in stable angina (PISA) study.

Aims: A meta-analysis of 13 randomized placebo-controlled trials demonstrated a benefit for dipyridamole therapy, particularly with longer duration of treatment. Although the mechanism of this effect is not well understood, dipyridamole increases endogenous tissue adenosine, which may have a beneficial effect on myocardial perfusion. Therefore, we measured the effects of dipyridamole on myocardial blood flow (MBF) and coronary flow reserve (CFR) by using positron emission tomography and H2O in patients with coronary artery disease.

Basal and hyperaemic myocardial blood flow in regionally denervated canine hearts: an in vivo study with positron emission tomography.

Purpose: Positron emission tomography (PET) studies in patients with diabetic autonomic neuropathy (DAN) have demonstrated the impact of this disease on cardiac sympathetic innervation and myocardial blood flow (MBF). To investigate the effects of selective partial sympathetic denervation of the left ventricle (LV) on baseline and hyperaemic MBF, we measured myocardial presynaptic catecholamine re-uptake (uptake-1), beta-adrenoceptor (beta-AR) density and MBF non-invasively by means of PET in a canine model of regional sympathetic denervation.

Methods: In 11 anaesthetised dogs, the sympathetic nerves of the free wall and septum of the LV were removed by means of dissection and phenol painting.

Comparison of myocardial blood flow and coronary flow reserve during dobutamine and adenosine stress: Implications for pharmacologic stress testing in coronary artery disease.

Background: Mechanistic differences between pharmacologic stressors may offer different clinical benefits. Therefore the effects of dobutamine and adenosine on absolute myocardial blood flow (MBF) and coronary flow reserve (CFR) were compared.

Methods And Results: We divided 36 patients (mean age, 61 +/- 8 years) with coronary artery disease into 2 groups based on stenosis severity as follows: greater than 50% but less than 75% (n = 16) and greater than 75% (n = 20).

Occurrence of regional left ventricular dysfunction in patients undergoing standard and biofeedback dialysis.

Background: Cardiac failure and cardiovascular death are extremely prevalent in dialysis patients. Recurrent subclinical myocardial ischemia is important in the genesis of heart failure in nondialysis patients. We examined whether this phenomenon occurs in response to the stress of hemodialysis (HD).

Dobutamine-induced hyperaemia inversely correlates with coronary artery stenosis severity and highlights dissociation between myocardial blood flow and oxygen consumption.

Objectives: To compare the relationship between dobutamine myocardial blood flow (MBF), rate-pressure product (RPP) and stenosis severity in patients with coronary artery disease (CAD).

Methods: 27 patients with single-vessel CAD were allocated to three groups based on stenosis severity: group 1, 50-69% (n = 9); group 2, 70-89% (n = 9); and group 3, >or= 90% (n = 9). Nine normal volunteers served as controls.

Relevance of coronary microvascular flow impairment to long-term remodeling and systolic dysfunction in hypertrophic cardiomyopathy.

Objectives: This study sought to evaluate whether the entity of microvascular dysfunction, assessed by positron emission tomography (PET), predicts the long-term development of left ventricular (LV) remodeling and systolic dysfunction in hypertrophic cardiomyopathy (HCM).

Background: A subgroup of patients with HCM developed LV dilation and systolic impairment. A causal role of coronary microvascular dysfunction has been suggested as the underlying pathophysiological mechanism.

Respiratory gating of cardiac PET data in list-mode acquisition.

Purpose: Respiratory motion has been identified as a source of artefacts in most medical imaging modalities. This paper reports on respiratory gating as a means to eliminate motion-related inaccuracies in PET imaging.

Methods: Respiratory gating was implemented in list mode with physiological signal recorded every millisecond together with the PET data.

Quantification of subendocardial and subepicardial blood flow using 15O-labeled water and PET: experimental validation.

Unlabelled: The purpose of this study was to assess the feasibility and accuracy of quantifying subendocardial and subepicardial myocardial blood flow (MBF) and the relative coronary flow reserves (CFR) using (15)O-labeled water (H(2)(15)O) and 3-dimensional-only PET.

Methods: Eight pigs were scanned with H(2)(15)O and (15)O-labeled carbon monoxide (C(15)O) after partially occluding the circumflex (n = 3) or the left anterior descending (n = 5) coronary artery, both at rest and during hyperemia induced by intravenous dipyridamole. Radioactive microspheres were injected during each of the H(2)(15)O scans.

Diagnostic and clinical perspectives of fusion imaging in cardiology: is the total greater than the sum of its parts?

Positron emission tomography, cardiovascular magnetic resonance and multislice computed tomography have contributed to changing our pathophysiological understanding of many conditions. Clinically, they have provided new tools for the identification of preclinical disease and a better understanding of how disease progresses. The application of these imaging modalities to preclinical disease and the use of these techniques in patients with overt cardiovascular disease are reviewed.

Rigid-body transformation of list-mode projection data for respiratory motion correction in cardiac PET.

High-resolution cardiac PET imaging with emphasis on quantification would benefit from eliminating the problem of respiratory movement during data acquisition. Respiratory gating on the basis of list-mode data has been employed previously as one approach to reduce motion effects. However, it results in poor count statistics with degradation of image quality.