Biomedical subjects

Alexandru Naum

Publications and source records attributed to Alexandru Naum.

7 recordsLinked to original sources

PubMed2006

Coronary artery flow velocity profile measured by transthoracic Doppler echocardiography predicts myocardial viability after acute myocardial infarction.

OBJECTIVE: To study whether flow velocity profile in the left anterior descending coronary artery (LAD) measured by transthoracic Doppler echocardiography (TTDE) predicts myocardial viability after reperfused anterior acute myocardial infarction (AMI). PATIENTS AND METHODS: 15 patients who had their first anterior ST elevation AMI and were successfully reperfused by coronary angioplasty and five controls without coronary artery disease were selected. Blood flow velocity spectrum was measured from the mid-LAD by TTDE 3 days after coronary angioplasty. Myocardial viability in the LAD region was quantified 3 months after AMI by relative uptake of 18F-fluorodeoxyglucose (FDG) imaged with positron emission tomography. Myocardium was graded as viable, partially viable or non-viable (relative FDG uptake >85%, 67-85% and <67%, respectively). Main outcome measures were diastolic deceleration time (DDT) of LAD flow velocity 3 days after AMI and myocardial viability 3 months after AMI. RESULTS: DDT of LAD flow velocity correlated with myocardial FDG uptake in the LAD region (r = 0.91, p<0.01). DDT was markedly longer in patients with viable myocardium (876+/-76 ms, n = 3) than partially viable (356+/-89 ms, n = 6, p<0.01), or non-viable myocardium (128+/-13 ms, n = 6, p<0.01). In controls, DDT was comparable (909+/-76 ms, n = 5) to patients with viable myocardium. DDT <190 ms was always associated with non-viable myocardium. CONCLUSIONS: DDT of LAD flow velocity is strongly associated with myocardial viability after reperfused anterior AMI. Non-invasive TTDE of the LAD may be used in the acute phase to predict long-term viability of the jeopardised myocardium.

Blood Flow Velocity↗

PubMed2006

Free fatty acid depletion acutely decreases cardiac work and efficiency in cardiomyopathic heart failure.

BACKGROUND: Metabolic modulators that enhance myocardial glucose metabolism by inhibiting free fatty acid (FFA) metabolism may improve cardiac function in heart failure patients. We studied the effect of acute FFA withdrawal on cardiac function in patients with heart failure caused by idiopathic dilated cardiomyopathy (IDCM). METHODS AND RESULTS: Eighteen fasting nondiabetic patients with IDCM (14 men, 4 women, aged 58.8+/-8.0 years, ejection fraction 33+/-8.8%) and 8 matched healthy controls underwent examination of myocardial perfusion and oxidative and FFA metabolism, before and after acute reduction of serum FFA concentrations by acipimox, an inhibitor of lipolysis. Metabolism was monitored by positron emission tomography and [15O]H2O, [11C]acetate, and [11C]palmitate. Left ventricular function and myocardial work were echocardiographically measured, and efficiency of forward work was calculated. Acipimox decreased myocardial FFA uptake by >80% in both groups. Rate-pressure product and myocardial perfusion remained unchanged, whereas stroke volume decreased similarly in both groups. In the healthy controls, reduced cardiac work was accompanied by decreased oxidative metabolism (from 0.071+/-0.019 to 0.055+/-0.016 min(-1), P<0.01). In IDCM patients, cardiac work fell, whereas oxidative metabolism remained unchanged and efficiency fell (from 35.4+/-12.6 to 31.6+/-13.3 mm Hg x L x g(-1), P<0.05). CONCLUSIONS: Acutely decreased serum FFA depresses cardiac work. In healthy hearts, this is accompanied by parallel decrease in oxidative metabolism, and myocardial efficiency is preserved. In failing hearts, FFA depletion did not downregulate oxidative metabolism, and myocardial efficiency deteriorated. Thus, failing hearts are unexpectedly more dependent than healthy hearts on FFA availability. We propose that both glucose and fatty acid oxidation are required for optimal function of the failing heart.

Aged↗

PubMed2006

Simultaneous evaluation of myocardial blood flow, cardiac function and lung water content using [15O]H2O and positron emission tomography.

PURPOSE: This study sought to evaluate an imaging approach using [15O]H2O and positron emission tomography (PET) for simultaneous assessment of myocardial perfusion, cardiac function and lung water content as a potential indicator of pulmonary oedema. METHODS: Twenty-six subjects divided into two groups (group I, 13 patients with idiopathic dilated cardiomyopathy; group II, 13 healthy volunteers) underwent dynamic PET scanning after intravenous infusion of approximately 995 MBq [15O]H2O. In both groups, echocardiograms were performed after the PET studies. From the dynamic [15O]H2O data, lung water content (LWC) at equilibrium, myocardial blood flow (MBF), cardiac output (CO), stroke volume (SV) and stroke volume indexes (SVI) using the indicator dilution principle were determined. RESULTS: LWC was 18% (p = 0.038) higher in patients than in controls. Global MBF did not differ significantly between the groups, but regional MBF values were significantly lower (p < 0.05) in the anterior and septal walls in the patient group. The results of the Passing-Bablok regression indicated the absence of a systematic difference between the two techniques. Bland-Altman analysis performed for each group (patients vs healthy controls) showed a non-significant bias (p > 0.1) of -0.02 +/- 0.82 vs -0.05 +/- 0.54 l/min (CO), -1.44 +/- 14.31 vs 1.70 +/- 10.56 ml/beat (SV) and 0.47 +/- 6.21 vs 0.30 +/- 5.02 ml/beat/m2 (SVI). The 95% limits of agreement were -1.62 to 1.59 vs -1.11 to 1.01 l/min (CO), -26.61 to 29.49 vs -22.39 to 18.99 ml/beat (SV) and -11.69 to 12.88 vs -9.53 to 10.14 ml/beat/m2 (SVI). Right ventricular CO was increased by 33% (p = 0.014) in the patient group as compared with normal controls. CONCLUSION: Our results demonstrate that additional analysis of cardiac function and lung water content are feasible from the dynamic cardiac [15O]H2O PET studies acquired for myocardial perfusion. The parameters appear to work as expected. Further studies are warranted to elucidate the clinical value of these new parameters.

Body Water↗

PubMed2006

Decreased myocardial free fatty acid uptake in patients with idiopathic dilated cardiomyopathy: evidence of relationship with insulin resistance and left ventricular dysfunction.

BACKGROUND: Results on myocardial substrate metabolism in the failing heart have been contradictory. Insulin resistance, a common comorbidity in heart failure patients, and medical therapy may modify myocardial metabolism in complex fashions. Therefore, we characterized myocardial oxidative and free fatty acid (FFA) metabolism in patients with idiopathic dilated cardiomyopathy (IDCM) and investigated the contributions of insulin resistance and beta-blocker therapy. METHODS AND RESULTS: Nineteen patients with IDCM (age 58 +/- 8 years, ejection fraction 33 +/- 8.8%) and 15 healthy controls underwent examination of myocardial blood perfusion, oxidative and FFA metabolism using positron emission tomography and [(15)O]H(2)O, [(11)C]acetate and [(11)C]palmitate, respectively. Echocardiography was used to assess myocardial function, work, and efficiency of forward work. Insulin resistance was calculated using the homeostasis model assessment index (HOMA index) and the degree of beta-blockade was estimated with a beta-adrenoceptor occupancy test. IDCM patients were characterized by decreased cardiac efficiency (35 +/- 2 versus 57 +/- 12 mm Hg.L.g(-1), P < .0001) and reduced myocardial FFA uptake (5.5 +/- 2.0 versus 6.4 +/- 1.2 mumol.100 g(-1).min(-1), P < .05), but the FFA beta-oxidation rate constant was not changed. In the patients, myocardial FFA uptake was inversely associated with left ventricular (LV) ejection fraction (r = -0.63, P < .01), indicating that further depression of LV function induces an opposite switch to greater FFA uptake. The FFA beta-oxidation rate constant correlated positively with the HOMA index (r = 0.53, P < .05). In patients on beta-1 selective beta-blockers, beta-1 adrenoceptor occupancy correlated inversely with LV work, oxidative metabolism, and FFA uptake; similar relationships were not found in patients on nonselective beta-blocker. CONCLUSIONS: Myocardial FFA metabolism is reduced in patients with IDCM. However, when LV function is further depressed and insulin resistance manifested, myocardial FFA uptake and oxidation are, in turn, upregulated. These findings may partly explain the discrepancies between previous studies about cardiac metabolism in heart failure.

Adrenergic beta-Antagonists↗

PubMed2005

Motion detection and correction for dynamic ( 15)O-water myocardial perfusion PET studies.

PURPOSE: Patient motion during dynamic PET studies is a well-documented source of errors. The purpose of this study was to investigate the incidence of frame-to-frame motion in dynamic ( 15)O-water myocardial perfusion PET studies, to test the efficacy of motion correction methods and to study whether implementation of motion correction would have an impact on the perfusion results. METHODS: We developed a motion detection procedure using external radioactive skin markers and frame-to-frame alignment. To evaluate motion, marker coordinates inside the field of view were determined in each frame for each study. The highest number of frames with identical spatial coordinates during the study were defined as "non-moved". Movement was considered present if even one marker changed position, by one pixel/frame compared with reference, in one axis, and such frames were defined as "moved". We tested manual, in-house-developed motion correction software and an automatic motion correction using a rigid body point model implemented in MIPAV (Medical Image Processing, Analysis and Visualisation) software. After motion correction, remaining motion was re-analysed. Myocardial blood flow (MBF) values were calculated for both non-corrected and motion-corrected datasets. RESULTS: At rest, patient motion was found in 18% of the frames, but during pharmacological stress the fraction increased to 45% and during physical exercise it rose to 80%. Both motion correction algorithms significantly decreased (p<0.006) the number of moved frames and the amplitude of motion (p<0.04). Motion correction significantly increased MBF results during bicycle exercise (p<0.02). At rest or during adenosine infusion, the motion correction had no significant effects on MBF values. CONCLUSION: Significant motion is a common phenomenon in dynamic cardiac studies during adenosine infusion but especially during exercise. Applying motion correction for the data acquired during exercise clearly changed the MBF results, indicating that motion correction is required for these studies.

Adult↗

PubMed2004

Assessment of right ventricular oxidative metabolism by PET in patients with idiopathic dilated cardiomyopathy undergoing cardiac resynchronization therapy.

PURPOSE: Right ventricular (RV) performance is known to have prognostic value in patients with congestive heart failure (CHF). Cardiac resynchronization therapy (CRT) has been found to enhance left ventricular (LV) energetics and metabolic reserve in patients with heart failure. The interplay between the LV and RV may play an important role in CRT response. The purpose of the study was to investigate RV oxidative metabolism, metabolic reserve and the effects of CRT in patients with CHF and left bundle brach block. In addition, the role of the RV in the response to CRT was evaluated. METHODS: Ten patients with idiopathic dilated cardiomyopathy who had undergone implantation of a biventricular pacemaker 8+/-5 months earlier were studied under two conditions: CRT ON and after CRT had been switched OFF for 24 h. Oxidative metabolism was measured using [11C]acetate positron emission tomography (Kmono). The measurements were performed at rest and during dobutamine-induced stress (5 microg/kg per minute). LV performance and interventricular mechanical delay (interventricular asynchrony) were measured using echocardiography. RESULTS: CRT had no effect on RV Kmono at rest (ON: 0.052+/-0.014, OFF: 0.047+/-0.018, NS). Dobutamine-induced stress increased RV Kmono significantly under both conditions but oxidative metabolism was more enhanced when CRT was ON (0.076+/-0.026 vs 0.065+/-0.027, p=0.003). CRT shortened interventricular delay significantly (45+/-33 vs 19+/-35 ms, p=0.05). In five patients the response to CRT was striking (32% increase in mean LV stroke volume, range 18-36%), while in the other five patients no response was observed (mean change +2%, range -6% to +4%). RV Kmono and LV stroke volume response to CRT correlated inversely (r=-0.66, p=0.034). None of the other measured parameters, including all LV parameters and electromechanical parameters, were associated with the response to CRT. In responders, RV Kmono with CRT OFF was significantly lower than in non-responders (0.036+/-0.01 vs 0.058+/-0.02, p=0.047). CONCLUSION: CRT appears to enhance RV oxidative metabolism and metabolic reserve during stress. Patients responding to CRT appear to have lower RV oxidative metabolism at rest, suggesting that the RV plays a significant role in the response to CRT.

Acetates↗

PubMed2004

The effects of cardiac resynchronization therapy on left ventricular function, myocardial energetics, and metabolic reserve in patients with dilated cardiomyopathy and heart failure.

OBJECTIVES: The effects of long-term cardiac resynchronization therapy (CRT) on left ventricular (LV) energetics and metabolic reserve were evaluated. BACKGROUND: Cardiac resynchronization therapy is a new therapy for patients with drug-refractory severe heart failure (HF). METHODS: Ten patients with idiopathic dilated cardiomyopathy who had undergone implantation of biventricular pacemaker 8 +/- 5 months earlier were studied during two conditions: CRT switched on, and after CRT was switched off for 24 h. Left ventricular function was measured using echocardiography and oxidative metabolism using [(11)C]acetate positron emission tomography. Both measurements were performed at rest and during dobutamine-induced stress (5 microg/kg/min). Basal- and adenosine-stimulated (140 microg/kg/min) myocardial blood flow were quantitated using [(15)O]water. RESULTS: During CRT off, LV stroke volume was significantly reduced at rest (72 +/- 18 ml vs. 63 +/- 15 ml, p < 0.05), but LV oxidative metabolism (K(mono)) remained unchanged (0.046 +/- 0.008 vs. 0.054 +/- 0.016 min(-1)) leading to a significant deterioration of myocardial efficiency of forward work (from 48.2 +/- 16.7 to 36.6 +/- 11.7 mm Hg.l/g, p < 0.05). During dobutamine-induced stress, stroke volume and K(mono) values were not different whether CRT was on or off. However, myocardial efficiency (56.1 +/- 16.1 vs. 49.8 +/- 18.0 mm Hg.ml.g(-1).min(-1), p = 0.099) and metabolic reserve, the response of K(mono) to dobutamine (0.023 +/- 0.014 vs. 0.013 +/- 0.014 min(-1), p = 0.09), tended to reduce when CRT was switched off. Cardiac resynchronization therapy had no effects on myocardial perfusion. Natriuretic peptides increased significantly during CRT-off period. CONCLUSIONS: Long-term CRT has beneficial effects on LV function and myocardial efficiency at rest in patients with HF. These effects are not associated with changes in myocardial perfusion or oxygen consumption. During dobutamine-induced stress, CRT does not affect functional parameters, but myocardial efficiency and metabolic reserve may be increased.

Carbon Radioisotopes↗