Sakae Shouda

Cardiac Autonomic Neuropathy in Patients with Chronic Renal Failure on Hemodialysis

To characterize uremic cardiac autonomic neuropathy, we measured plasma catecholamines, analyzed the 24-hour heart rate variability (HRV), and acquired serial images with 123I-metaiodobenzylguanidine (MIBG) in 44 patients with chronic renal failure on hemodialysis and in 14 controls. Time-domain measures were calculated using the Marquette HRV program. MIBG clearance rates from the heart and lung were evaluated on planar images, and the regional MIBG uptake in the left ventricular myocardium was evaluated with single-photon emission computed tomography. Compared with controls, plasma dopamine and norepinephrine levels were elevated (p < 0.001 and p = 0.03, respectively), and all the time-domain measures of HRV were reduced in the patients (p < 0.001). The MIBG clearance rate from the heart was higher (p < 0.001), that from the lung was lower (p < 0.001), and the myocardial MIBG distribution was more heterogeneous in patients than in controls (total uptake score p ≤ 0.03). These variables were similar between 26 patients without and 18 patients with hypertension. Uremic cardiac autonomic neuropathy may be characterized by high plasma levels of dopamine and norepinephrine, reduced HRV, and abnormal MIBG kinetics in the heart with heterogeneous myocardial MIBG distribution, suggesting cardiac sympathetic overactivity and parasympathetic deterioration. In addition, abnormal MIBG kinetics in the lung may imply pulmonary sympathetic nervous dysfunction and/or endothelial dysfunction in uremic patients.

Diabetic cardiac autonomic dysfunction: Parasympathetic versus sympathetic

BackgroundDiabetic cardiac autonomic dysfunction often causes lethal arrhythmia and sudden cardiac death.123I-Metaiodobenzylguanidine (MIBG) can evaluate cardiac sympathetic dysfunction, and analysis of heart rate variability (HRV) can reflect cardiac parasympathetic activity. We examined whether cardiac parasympathetic dysfunction assessed by HRV may correlate with sympathetic dysfunction assessed by MIBG in diabetic patients.Methods and ResultsIn 24-hour electrocardiography, we analyzed 4 HRV parameters: high-frequency power (HF), HF in the early morning (EMHF), rMSSD and pNN50. MIBG planar images and SPECT were obtained 15 minutes (early) and 150 minutes (late) after injection and the heart washout rate was calculated. The defect score in 9 left ventricular regions was scored on a 4 point scale (0 = normal ∼ 3 = severe defect). In 20 selected diabetic patients without congestive heart failure, coronary artery disease and renal failure, parasympathetic HRV parameters had a negative correlation with the sum of defect scores (DS) in the late images (R = −0.47 ∼ −0.59, p < 0.05) and some parameters had a negative correlation with the washout rate (R = −0.50 ∼ −0.55, p < 0.05). In a total of 64 diabetic patients also, these parameters had a negative correlation with late DS (R = −0.28 ∼ −0.35, p < 0.05) and early DS (R = −0.27 ∼ −0.32, p < 0.05).ConclusionsThe progress of diabetic cardiac parasympathetic dysfunction may parallel the sympathetic one.

Comparison of [123I]metaiodobenzylguanidine kinetics with heart rate variability and plasma norepinephrine level

Background[123I]Metaiodobenzylguanidine (MIBG) imaging has been used to assess cardiac sympathetic nerve abnormalities. We evaluated the clinical significance of myocardial MIBG imaging as a measure of cardiac sympathetic nervous system function by comparing it to heart rate variability and plasma norepinephrine level.Methods and ResultsIn 211 subjects, we analyzed heart rate variability with 24-hour electrocardiography, performed scintigraphy with MIBG, and measured plasma norepinephrine levels. Time and frequency domain measures of heart rate variability were calculated with the Marquette heart rate variability program (Marquette Electronics, Milwaukee, Wis.). Early and late myocardial MIBG uptakes were measured at 15 and 150 minutes after injection, respectively. MIBG clearance rate from the heart and heart-to-lung and heart-to-mediastinum ratios of MIBG activities were calculated. On the whole, heart rate variability, including low-frequency power, correlated positively, but modestly so, with late MIBG uptake and negatively with MIBG clearance rate. The plasma norepinephrine level correlated negatively with late MIBG uptake and with heart rate variability, including low-frequency power, and positively with MIBG clearance rate. Similar correlations were also observed in patient subgroups with coronary artery disease, diabetes mellitus, and renal failure, but these correlations were weak (R2<0.5).ConclusionsIncreased cardiac sympathetic nervous system activity may be associated with increased myocardial MIBG clearance and decreased heart rate variability, including low-frequency power. Because these associations were not strong, however, the combination of heart rate variability with MIBG may allow an interactive assessment of the cardiac autonomic nervous system.

Quantification of left ventricular size on exercise thallium-201 single-photon emission tomography

The purposes of this study were to determine whether quantification of the left ventricular size on exercise thallium-201 single-photon emission tomography (SPET) correlates with echocardiographic measurements, whether the quantification reflects the severity of coronary artery disease, and whether it can provide supplementary information regarding the severity of coronary artery disease. In 42 control subjects and 110 patients who underwent coronary angiography, we performed exercise201Tl SPET and quantified six non-regional markers: lung201Tl uptake on an initial planar image (Lung/Heart), left ventricular width on a tomogram (Width), change in the Width from the initial to delayed tomograms (ΔWidth), count ratio of the left ventricular cavity to the myocardium (C/M), count ratio of the lung to the myocardium (UM), and count ratio of the lung to the left ventricular cavity (L/C). In 76 patients, furthermore, the Width was compared with echocardiographic measurements. The Width correlated with echocardiographic measurements (P<0.001). The Width and ΔWidth were significantly different among zero-, one-, two- and three-vessel disease (P<0.001). However, the Width and ΔWidth could not improve the power of discrimination for multi-vessel disease derived from the Lung/Heart. The six non-regional markers correlated with each other (P<0.001). Among the six markers, the Lung/Heart was only the independent discriminator for multi-vessel disease. In conclusion, quantification of the left ventricular size on exercise201Tl SPET correlated with echocardiographic measurements and reflected the severity of coronary artery disease, but may be replaced with quantitation of the lung201Tl uptake.

Usefulness of measurement of plasma atrial natriuretic peptide levels in exercise testing of patients with coronary heart disease

Atrial natriuretic peptide secretion on exercise testing may be exaggerated by left ventricular dysfunction due to multivessel coronary disease rather than by scintigraphically detectable myocardial ischemia. The measurement of plasma atrial natriuretic peptide levels during exercise test may provide additional information regarding the severity of coronary heart disease.