Kei Tawarahara

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.

Exercise testing and thallium-201 emission computed tomography in patients with intraventricular conduction disturbances

The specificity of exercise thallium-201 emission computed tomography for coronary artery disease was assessed in patients with intraventricular conduction disturbances. Eighty-seven patients were studied: 33 with right bundle branch block (RBBB), 11 with RBBB and left-axis deviation, 11 with left (L)BBB, 12 on right ventricular pacing, and 20 with Wolff-Parkinson-White (WPW) syndrome. A control group of 349 consecutive patients with normal intraventricular conduction was also examined. The specificity of diagnosis of coronary artery disease in patients with LBBB (30%), right ventricular pacing (44%) or RBBB plus left-axis deviation (50%) was significantly lower than in patients with normal intraventricular conduction (94%; p less than 0.01). In contrast, there was no significant difference between specificity in patients with RBBB (86%) or WPW syndrome (90%) and patients with normal intraventricular conduction. Perfusion defects were found in the anterior, septal and inferior segments in patients with LBBB, and in the septal and inferior segments in patients with RBBB plus left-axis deviation despite the absence of coronary stenosis. Furthermore, diffuse slow washout was seen more often in patients with WPW syndrome (35%) than in controls who had normal intraventricular conduction (11%; p less than 0.05), despite a good exercise performance in the former group. This study suggests that there is an increased incidence of abnormal perfusion and clearance during exercise thallium-201 emission computed tomography in patients with intraventricular conduction disturbances.

Distribution of late gadolinium enhancement in end-stage hypertrophic cardiomyopathy and dilated cardiomyopathy: differential diagnosis and prediction of cardiac outcome.

BACKGROUND The prognostic implications of late gadolinium enhancement (LGE) have been evaluated in ischemic and non-ischemic cardiomyopathies. The present study analyzed LGE distribution in patients with end-stage hypertrophic cardiomyopathy (ES-HCM) and with dilated cardiomyopathy (DCM), and tried to identify high risk patients in DCM. METHODS Eleven patients with ES-HCM and 72 with DCM underwent cine- and LGE-cardiac magnetic resonance and ultrasound cardiography. The patient outcome was analyzed retrospectively for 5years of follow-up. RESULTS LGE distributed mainly in the inter-ventricular septum, but spread more diffusely into other left ventricular segments in patients with ES-HCM and in a certain part of patients with DCM. Thus, patients with DCM can be divided into three groups according to LGE distribution; no LGE (n=24), localized LGE (localized at septum, n=36), and extensive LGE (spread into other segments, n=12). Reverse remodeling occurred after treatment in patients with no LGE and with localized LGE, but did not in patients with extensive LGE and with ES-HCM. The event-free survival rate for composite outcome (cardiac death, hospitalization for decompensated heart failure or ventricular arrhythmias) was lowest in patients with extensive LGE (92%, 74% and 42% in no LGE, localized LGE, and extensive LGE, p=0.02 vs. no LGE), and was comparable to that in patients with ES-HCM (42%). CONCLUSIONS In DCM, patients with extensive LGE showed no functional recovery and the lowest event-free survival rate that were comparable to patients with ES-HCM. The analysis of LGE distribution may be valuable to predict reverse remodeling and to identify high-risk patients.

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.

Evaluation of right and left ventricular function by quantitative blood-pool SPECT (QBS): Comparison with conventional methods and quantitative gated SPECT (QGS)

Though quantitative ECG-gated blood-pool SPECT (QBS) has become a popular tool in research settings, more verification is necessary for its utilization in clinical medicine. To evaluate the reliability of the measurements of left and right ventricular functions with QBS, we performed QBS, as well as first-pass pool (FPP) and ECG-gated blood-pool (GBP) studies on planar images in 41 patients and 8 healthy volunteers. Quantitative ECG-gated myocardial perfusion SPECT (QGS) was also performed in 30 of 49 subjects. First, we assessed the reproducibility of the measurements of left and right ventricular ejection fraction (LVEF, RVEF) and left and right ventricular end-diastolic volume (LVEDV, RVEDV) with QBS. Second, LVEF and RVEF obtained from QBS were compared with those from FPP and GBP, respectively. Third, LVEF and LVEDV obtained from QBS were compared with those from QGS, respectively. The intra- and inter-observer reproducibilities were excellent for LVEF, LVEDV, RVEF and RVEDV measured with QBS (r = 0.88 to 0.96, p < 0.01), while the biases in the measurements of RVEF and RVEDV were relatively large. LVEF obtained from QBS correlated significantly with those from FPP and GBP, while RVEF from QBS did not. LVEF and LVEDV obtained from QBS were significantly correlated with those from QGS, but the regression lines were not close to the lines of identity. In conclusion, the measurements of LVEF and LVEDV with QBS have good reproducibility and are useful clinically, while those of RVEF and RVEDV are less useful compared with LVEF and LVEDV. The algorithm of QBS for the measurements of RVEF and RVEDV remains to be improved.

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.

Functional, morphological and electrocardiographical abnormalities in patients with apical hypertrophic cardiomyopathy and apical aneurysm: correlation with cardiac MR.

Objective The prognosis of apical hypertrophic cardiomyopathy (APH) has been benign, but apical myocardial injury has prognostic importance. We studied functional, morphological and electrocardiographical abnormalities in patients with APH and with apical aneurysm and sought to find parameters that relate to apical myocardial injury. Methods Study design: a multicentre trans-sectional study. Patients: 45 patients with APH and 5 with apical aneurysm diagnosed with transthoracic echocardiography (TTE) in the database of Hamamatsu Circulation Forum. Measure: the apical contraction with cine-cardiac MR (CMR), the myocardial fibrotic scar with late gadolinium enhancement (LGE)-CMR, and QRS fragmentation (fQRS) defined when two ECG-leads exhibited RSR’s patterns. Results Cine-CMR revealed 27 patients with normal, 12 with hypokinetic and 11 with dyskinetic apical contraction. TTE misdiagnosed 11 (48%) patients with hypokinetic and dyskinetic contraction as those with normal contraction. Apical LGE was apparent in 10 (83%) and 11 (100%) patients with hypokinetic and dyskinetic contraction, whereas only in 11 patients (41%) with normal contraction (p<0.01). Patients with dyskinetic apical contraction had the lowest left ventricular ejection fraction, the highest prevalence of ventricular tachycardia, and the smallest ST depression and depth of negative T waves. The presence of fQRS was associated with impaired apical contraction and apical LGE (OR=8.32 and 8.61, p<0.05). Conclusions CMR is superior to TTE for analysing abnormalities of the apex in patients with APH and with apical aneurysm. The presence of fQRS can be a promising parameter for the early detection of apical myocardial injury.

Exercise myocardial perfusion scintigraphy is useful for evaluating myocardial ischemia even in the elderly

Pharmacologic stress testing is recommended to elderly patients as a valuable alternative to exercise testing. We examined whether exercise testing is as useful for evaluating myocardial ischemia in the elderly as in the young. The consecutive 1,508 patients who underwent exercise201Tl single-photon emission computed tomography (SPECT) were divided into six age groups: 6–29 years (n =56), 30–44 (n=143), 45–54 (n=311), 55–64 (n=498), 65–74 (n=402), and 75–88 (n=98). Both heart rate and rate-pressure product at peak exercise were significantly lower in patients aged 75–88 than in the other five groups. The frequency of ischemic ST depression was higher in patients aged 75–88 than in those aged 6–74, although the difference was not significant. Moreover, the frequency of201Tl transient defect was significantly higher in patients aged 75–88 than in those aged 6–74. On the other hand, the sensitivity of ischemic ST depression for201 Tl transient defect was similar among the six groups, but the specificity was significantly lower in patients aged 75–88 than in those aged 6–74. In conclusion, exercise201Tl SPECT is useful for evaluating myocardial ischemia even in the elderly, but exercise electrocardiography has limitations such as lower specificity in the elderly than201Tl SPECT.

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.

The Diagnosis of Spontaneous Coronary Artery Dissection by Optical Coherence Tomography

Spontaneous coronary artery dissection (SCAD) is rare, but it frequently presents as acute myocardial infarction. It is frequently fatal and most cases are diagnosed at autopsy. We herein present the case of a 65-year-old woman with ST-elevation and myocardial infarction due to SCAD. Optical coherence tomography (OCT) helped us to confirm the diagnosis. The information on the intravascular morphology provided by OCT imaging is much more detailed in comparison to that provided by coronary angiography (CAG) and intravascular ultrasound (IVUS).