Dopamine-induced migrating myoelectrical complex-like activity in human duodenum

The effect of dopamine on human gastric and small intestinal interdigestive motility was investigated in 12 subjects. Intestinal motility was recorded by means of a four-lumen polyvinyl probe with four open tips located 15 cm apart, continuously perfused with distilled water. In each subject during the same study, after recording two consecutive spontaneous phase III of migrating myoelectrical complexes and when a phase II appeared, dopamine was infused intravenously twice in a dose of 5 g/kg/min for 15 min with an interval of 20 min between each infusion. In six subjects, the second dopamine infusion was preceded by a treatment with sulpiride (10 mg, intravenously, as bolus) or domperidone (10 mg, intravenously, as bolus), each considered a highly selective dopamine antagonist. The results show that dopamine stimulates duodenal motility producing a pattern similar to that observed in phase III of spontaneously occurring migrating myoelectrical complexes. The second dopamine infusion reproduced in all cases the same pattern of motility as observed during the first infusion. Sulpiride and domperidone prevented the effect of dopamine in all cases. It is therefore suggested that dopamine-induced duodenal motility may involve specific dopaminergic receptors.     

Determinants of left ventricular mechanical dyssynchrony in patients submitted to myocardial perfusion imaging: A cardiac CZT study

Background

An interaction between coronary anatomy, myocardial perfusion, and left ventricular (LV) functional parameters in the development of mechanical LV dyssynchrony (LVD) has been suggested. This study examined the correlates of LVD in a large sample size of patients with known or suspected coronary artery disease (CAD) using cadmium-zinc-telluride camera.

Methods

Six-hundred and fifty-seven consecutive patients who underwent myocardial perfusion imaging (MPI) and coronary angiography were included. Coronary stenosis >70% was considered significant. LV perfusion and functional parameters were computed from MPI images. The presence of significant LVD was evaluated by phase standard deviation and histogram bandwidth.

Results

415/657 (63%) patients had significant CAD. LVD was present in 247 (38%) patients and was associated with the presence of a higher CAD burden (P < .001), more impaired measures of LV perfusion (P < .001), contractile function (P < .001), and larger LV volumes (P < .001). By multivariate analysis, the LV end-systolic volume index (P < .001) and ischemic burden (P < .001) were the strongest predictors of LVD independent of CAD extent and LV systolic dysfunction.

Conclusions

LVD is frequent in patients undergoing MPI for suspected or known CAD. Its presence is independent of CAD burden and LV systolic dysfunction, but is dependent on the presence of myocardial perfusion abnormalities and LV end-systolic volume.

     

Extension of myocardial necrosis differently affects MIBG retention in heart failure caused by ischaemic heart disease or by dilated cardiomyopathy

Purpose This study aims to investigate the relationship between cardiac sympathetic nervous function (CSNF) and myocardial perfusion/function in patients with heart failure (HF) due to dilated cardiomyopathy (DCM) or ischaemic heart disease (CAD).Methods Twenty patients (10 DCM, 10 CAD, 17 males, age 69±5 years) with NYHA class IIIb HF were studied. CSNF was evaluated by early/delayed ¹²³I-metaiodobenzylguanidine (MIBG) uptake and regional washout (WO). Myocardial perfusion and function were evaluated by ^99mTc-tetrofosmin gated single-photon emission tomography (G-SPECT) using a 20-segment model for 400 segments. In each segment, regional MIBG WO was computed as (count density in early images–count density in delayed images/count density in early images)×100.Results DCM and CAD showed similar summed rest perfusion score (6.7±5 vs 9.5±5, p=NS) and mean ejection fraction values (29±7% vs 30±9%, p=NS). By contrast, the summed thickening score was higher in DCM than in CAD patients (26±7 vs 17±6, p<0.05). QGS analysis identified akinesis/dyskinesis in 129/137 (94%) severely hypoperfused segments which were considered as damaged. According to the underlying aetiology of HF, marked differences in regional MIBG WO were observed. In fact, within the CAD group, regional MIBG WO was lower in reference than in damaged segments (38±21% vs 46±19%, p<0.05). By contrast, in DCM patients, regional MIBG WO was faster in reference than in damaged segments (49±18% vs 41±30%, p<0.05). When the two groups were directly compared, regional MIBG WO from damaged areas was similar irrespective of the underlying disease, while it was faster in DCM than in CAD patients from reference segments.Conclusion These data confirm the hypothesis that the presence of myocardial necrosis in HF due to CAD and the consequent loss of neuronal endings cause alterations in regional MIBG WO different from those observed in DCM.     

High diagnostic accuracy of low-dose gated-SPECT with solid-state ultrafast detectors: preliminary clinical results

Purpose  

Appropriate use of SPECT imaging is regulated by evidence-based guidelines and appropriateness criteria in an effort to limit the burden of radiation administered to patients. We aimed at establishing whether the use of a low dose for stress–rest single-day nuclear myocardial perfusion imaging on an ultrafast (UF) cardiac gamma camera using cadmium-zinc-telluride solid-state detectors could be used routinely with the same accuracy obtained with standard doses and conventional cameras.     

Regional concordance and discordance between rest thallium 201 and sestamibi imaging for assessing tissue viability: Comparison with postrevascularization functional recovery

Background  

Whether the combined analysis of rest ²⁰¹Tl and sestamibi uptake provides additional information regarding myocardial viability in patients with coronary artery disease is still to be investigated.     

Association between left ventricular regional sympathetic denervation and mechanical dyssynchrony in phase analysis: a cardiac CZT study

Purpose

To evaluate the relationships among myocardial sympathetic innervation, perfusion and mechanical synchronicity assessed with cardiac cadmium-zinc-telluride (CZT) scintigraphy.

Methods

A group of 29 patients underwent an evaluation of myocardial perfusion with ^99mTc-tetrofosmin CZT scintigraphy and adrenergic innervation with ¹²³I-metaiodobenzylguanidine (MIBG) CZT scintigraphy. The summed rest score (SRS), motion score (SMS) and thickening score (STS), as well as the summed ¹²³I-MIBG defect score (SS-MIBG), were determined. Regional tracer uptake for both ^99mTc-tetrofosmin and ¹²³I-MIBG was also calculated. Finally, the presence of significant myocardial mechanical dyssynchrony was evaluated in phase analysis on gated CZT images and the region of latest mechanical activation identified.

Results

Significant mechanical dyssynchrony was present in 17 patients (59 %) and associated with higher SRS (P?=?0.030), SMS (P?<?0.001), STS (P?=?0.003) and early SS-MIBG (P?=?0.037) as well as greater impairments in left ventricular ejection fraction (P?<?0.001) and end-diastolic volume (P?<?0.001). In multivariate analysis a higher end-diastolic volume remained the only predictor of mechanical dyssynchrony (P?=?0.047). Interestingly, while in the whole population regional myocardial perfusion and adrenergic activity were strongly correlated (R?=?0.68), in patients with mechanical dyssynchrony the region of latest mechanical activation was predicted only by greater impairment in regional ¹²³I-MIBG uptake (P?=?0.012) that overwhelmed the effect of depressed regional perfusion.

Conclusion

Left ventricular mechanical dyssynchrony is associated with greater depression in contractile function and greater impairments in regional myocardial perfusion and sympathetic activity. In patients with dyssynchrony, the region of latest mechanical activation is characterized by a significantly altered adrenergic tone.     

Myocardial imaging with <Superscript>99m</Superscript>Tc-Tetrofosmin: Influence of post-stress acquisition time,regional radiotracer uptake,and wall motion abnormalities on the clinical result

Background  

We previously demonstrated that early (15′, T1) post-stress myocardial imaging with Tetrofosmin could be more accurate than standard acquisitions (45′, T2) in identifying coronary artery disease.     

Relationship between myocardial perfusion abnormalities and contractile impairment in anginal patients

Background

A relationship between left ventricular (LV) contractile impairment and myocardial perfusion abnormalities has been suggested.

Methods and Results

Three-hundred and thirty-seven patients underwent myocardial perfusion imaging at CZT and coronary angiography. On scintigraphic images, the summed difference score (SDS) and LV-ejection fraction (EF) were computed. Patients were categorized as follows: Group-1 (LV-EF < 40%; 71 patients), Group-2 (LV-EF ≥ 40% and < 55%; 77 patients), and Group-3 (LV-EF ≥ 55%; 189 patients). Significant coronary artery disease (CAD; ≥50% stenosis) was recognized in 159/337 (47%) patients. Interestingly, while in Group-3 subjects an inverse relationship between SDS values and post-stress LV-EF was evident (P < .001), Group-1 patients presented a significant association between an increased SDS and more elevated post-stress LV-EF values (P = .009). Similarly, despite in the overall population an increasing severity of CAD was associated with higher SDS values (P < .001), this relationship disappeared in Group-1 patients (P = .298). At multiple regression analysis, after correction for CAD, LV dysfunction was negatively associated with an elevated SDS (P = .018). Conversely in patients with normal LV function and no history of myocardial infarction, CAD extent, and functional measures of stress-induced myocardial ischemia were strictly correlated.

Conclusions

Independently from CAD, a significantly impaired LV function associates with a lower prevalence of reversible ischemia.