Metabolic syndrome associates with left atrial dysfunction.

BACKGROUND AND AIMS: Obesity and metabolic syndrome (MetS) are risk factors of atrial fibrillation (AF), but limited data exist on their effect on left atrial (LA) function. The aim of the study was to evaluate the effects of cardiac, hepatic and intra-abdominal ectopic fat depots and cardiometabolic risk factors on LA function in non-diabetic male subjects. METHODS AND RESULTS: Myocardial and hepatic triglyceride contents were measured with 1.5T 1H-magnetic resonance spectroscopy and LA and left ventricular function, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), epicardial and pericardial fat by magnetic resonance imaging (MRI) in 33 men with MetS and 40 men without MetS. LA volumes were assessed using a novel three-chamber orientation based MRI approach. LA ejection fraction (EF) was lower in MetS patients than in the control group (44 ± 7.7% in MetS vs. 49 ± 8.6% in controls, p = 0.013) without LA enlargement, indicating LA dysfunction. LA EF correlated negatively with waist circumference, body mass index, SAT, VAT, fasting serum insulin, and homeostasis model assessment of insulin resistance index, and positively with fasting serum high-density lipoprotein cholesterol. VAT was the best predictor of reduced LA EF. CONCLUSIONS: MetS associates with subclinical LA dysfunction. Multiple components of MetS are related to LA dysfunction, notably visceral obesity and insulin resistance. Further studies are needed to elucidate the role of mechanical atrial remodeling in the development of AF.

Biomarkers and prediction of myocardial triglyceride content in non-diabetic men.

BACKGROUND AND AIMS: Lipid oversupply to cardiomyocytes or decreased utilization of lipids leads to cardiac steatosis. We aimed to examine the role of different circulating metabolic biomarkers as predictors of myocardial triglyceride (TG) content in non-diabetic men. METHODS AND RESULTS: Myocardial and hepatic TG contents were measured with 1.5 T magnetic resonance (MR) spectroscopy, and LV function, visceral adipose tissue (VAT), abdominal subcutaneous tissue (SAT), epicardial and pericardial fat by MR imaging in 76 non-diabetic men. Serum concentration of circulating metabolic biomarkers [adiponectin, leptin, adipocyte-fatty acid binding protein 4 (A-FABP 4), resistin, and lipocalin-2] including ß-hydroxybuturate (ß-OHB) were measured. Subjects were stratified by tertiles of myocardial TG into low, moderate, and high myocardial TG content groups. Concentrations of ß-OHB were lower (p = 0.003) and serum levels of A-FABP 4 were higher (p < 0.001) in the group with high myocardial TG content compared with the group with low myocardial TG content. ß-OHB was negatively correlated with myocardial TG content (r = -0.316, p = 0.006), whereas A-FABP 4 was not correlated with myocardial TG content (r = 0.192, p = 0.103). In multivariable analyses ß-OHB and plasma glucose levels were the best predictors of myocardial TG content independently of VAT and hepatic TG content. The model explained 58.8% of the variance in myocardial TG content. CONCLUSION: Our data showed that ß-OHB and fasting glucose were the best predictors of myocardial TG content in non-diabetic men. These data suggest that hyperglycemia and alterations in lipid oxidation may be associated with cardiac steatosis in humans.

Intraosseous access in neonates and infants: risk of severe complications - a case report.

Gaining vascular access in a neonate during cardiopulmonary resuscitation is crucial and challenging. Intraosseous (IO) access can offer a fast and reliable method for achieving emergency access for fluids and drugs when venous access fails in a critically ill child. IO access can however result in rare, but serious adverse events including compartment syndrome and amputation. We describe a case resulting in leg amputation due to IO infusion in a neonate after resuscitation and therapeutic hypothermia. We compared 10 tibia X-rays in three age groups. The mean medullary diameter of the proximal tibia at the recommended site for IO access was 7 mm in neonate, 10 mm in 1- to 12-month-old infants, and 12 mm in 3- to 4-year-old children. This provides a narrow margin of safety for the correct positioning and the avoidance of dislodgement of the IO needle. The correct position of the IO needle should be confirmed by bone marrow aspiration and fluid bolus. Unnecessary touching of the IO needle after fixing it in place should be avoided by inserting a luer-lock catheter with a three-way stop-cock for IO drug and fluid administration. Regular observation of the circulation and possible swelling of the leg should be performed. The IO administration of inotropic infusions should also be avoided after the initial resuscitation phase. When treating with therapeutic hypothermia, it may be wise to remove the IO needle much earlier than the currently recommended 24 h because of the problems in peripheral circulation and its monitoring.

Electrocardiographic changes associated with insulin resistance.

BACKGROUND AND AIM: Cardiac steatosis has been related to increased risk of heart disease. We investigated the association between cardiac steatosis, electrocardiographic (ECG) abnormalities, and individual components of the metabolic syndrome (MetS). METHODS AND RESULTS: A 12-lead ECG and laboratory data were examined in 31 men with the MetS and in 38 men without the MetS. Myocardial triglyceride (MTG) content was measured with 1.5 T magnetic resonance (MR) spectroscopy and epicardial and pericardial fat by MR imaging. MTG content, epicardial and pericardial fat depots were higher in men with the MetS compared with subjects without the MetS (p < 0.001). The heart rate was increased (p < 0.001), the PR interval was longer (p < 0.044), the frontal plane QRS axis shifted to the left (p < 0.001), and the QRS voltage (p < 0.001) was lower in subjects with the MetS. The frontal plane QRS axis and the QRS voltage were inversely correlated with MTG content, waist circumference (WC), body mass index (BMI), TGs, and fasting blood glucose. High-density lipoprotein cholesterol correlated positively and measures of insulin resistance negatively with the QRS voltage. MTG content and hypertriglyceridemia were determinants of the frontal plane QRS and WC and hyperglycemia were predictors of the QRS voltage. CONCLUSION: The MetS and cardiac steatosis appear to associate with multiple changes on 12-lead ECG. The frontal plane QRS axis is shifted to the left and the QRS voltage is lower in subjects with the MetS. Standard ECG criteria may underestimate the presence of left ventricular hypertrophy in obese subjects with cardiometabolic risk factors.

Comparison of current density viability imaging at rest with FDG-PET in patients after myocardial infarction.

The assessment of myocardial viability is a major diagnostic challenge in patients with coronary artery disease (CAD) after myocardial infarction. Novel threedimensional current density (CD) imaging algorithms use high-resolution magnetic field mapping to determine the electrical activity of myocardial segments at rest. We, for the first time, compared CD activity obtained with several algorithms to 18-F-fluoro-deoxyglucose positron emission tomography (FDG-PET) in evaluation of myocardial viability. Magnetic field maps were obtained in nine adult patients (pt) with CAD and a history of infarction. The criterion for non-viable myocardium was an FDG-PET uptake with less than 45% of the maximum in the respective segments. CD imaging was applied to the left ventricle by using six different methods to solve the inverse problem. Mean CD activity was calculated for a close meshed grid of 90 locations of the left ventricle. A cardiologist compared bull's eye plots of CD and FDG-PET activity by eye. Spearman's correlation coefficients and specificity at a given level of sensitivity (70%) were calculated. Bull's eye plots revealed a significant correlation of CD/PET in 5 pt and no correlation in 3 pt. One pt had a negative correlation. The six different CD reconstruction methods performed similar. While CD reconstruction has the principal potential to image viable myocardium, we found that the reconstructed CD magnitude was low in scar segments but also reduced in some segments with preserved metabolic activity under resting conditions. New vector measurement techniques, the use of additional stress testing and advances in mathematical methodology are expected to improve CD imaging in future.

Statin-treated familial hypercholesterolemia patients with coronary heart disease and pronounced atherosclerosis do not have more brain lesions than healthy controls in later middle age.

BACKGROUND: Clinically silent brain lesions detected with magnetic resonance imaging (MRI) are associated with increased risk for stroke, while stroke risk is controversial in familial hypercholesterolemia (FH). PURPOSE: To determine whether the occurrence and size of clinically silent brain lesions in FH patients with coronary heart disease (CHD) is higher than in neurologically healthy controls without CHD. MATERIAL AND METHODS: Brain MRI (1.5T) was performed on 19 DNA-test-verified FH patients with CHD and on 29 cardiovascularly and neurologically healthy controls, all aged 48 to 64 years. All patients were on cardiovascular medication. Intracranial arteries were evaluated by MR angiography. Infarcts, including lacunas, and white matter T2 hyperintensities (WMHI), considered as signs of small vessel disease, were recorded. A venous blood sample was obtained for assessment of risk factors. Carotid and femoral intima-media thicknesses (IMT), assessed with ultrasound, were indicators of overall atherosclerosis. RESULTS: On intracranial MR angiography, three patients showed irregular walls or narrowed lumens in intracranial carotid arteries. No silent infarcts appeared, and no differences in numbers or sizes of WMHIs between groups were recorded. Patients had greater carotid and femoral IMTs, and a greater number of carotid and femoral plaques. Cholesterol-years score, level of low-density lipoprotein (LDL) cholesterol, and level of high-sensitivity C-reactive protein (hsCRP) of the FH-North Karelia patients were higher than those of the controls, while the level of high-density lipoprotein (HDL) cholesterol in controls was higher. CONCLUSION: FH patients with CHD and adequate cardiovascular risk-factor treatment showed no difference in the amount or size of clinically silent brain lesions compared to controls, despite patients' more severe atherosclerosis.

Magnetic resonance imaging of the failing heart.

Validated cardiovascular magnetic resonance imaging procedures are available for assessment of myocardial functional and perfusion reserve, viability and extent of infarction. The techniques still under development provide opportunities for further research of both new treatment strategies and magnetic resonance imaging.

Assessment of the effect of endurance training on left ventricular relaxation with magnetic resonance imaging.

The purpose of the study was to assess the effect of endurance training on the early diastolic global and regional left ventricular (LV) relaxation with three magnetic resonance imaging (MRI) techniques. Fourteen subjects were examined with MRI before and after 3-month endurance training. Global early diastolic LV myocardial relaxation was assessed with mitral flow velocity mapping and regional LV early myocardial relaxation with myocardial tagging. LV end-diastolic and end-systolic volumes and mass were assessed with cine Magnetic resonance imaging (MRI). Mitral flow velocity mapping analysis revealed that the time to peak early filling shortened after training (before 112+/-32 ms, after 97+/-21, P<0.05), indicating more rapid global early myocardial relaxation. LV mass increased (97+/-19 g, 105+/-18, P<0.01) and end-systolic volume decreased (47+/-11 mL, 42+/-13, P<0.05). According to myocardial tagging analysis early myocardial relaxation in the septum and in the LV lateral wall increased (P<0.05). Regional tagging analysis showed enhanced myocardial relaxation in the basal septum (P<0.05). Global and regional LV early diastolic relaxation improved and physiological LV hypertrophy was found after the exercise training period for 3 months in healthy sedentary subjects.

Statistical shape model of atria, ventricles and epicardium from short- and long-axis MR images.

We describe a new 3-D statistical shape model of the heart consisting of atria, ventricles and epicardium. The model was constructed by combining information on standard short- and long-axis cardiac MR images. In the model, the variability of the shape was modeled with PCA- and ICA-based shape models as well as with non-parametric landmark probability distributions and a probabilistic atlas. The statistical atlas was built from 25 healthy subjects. The shape model was evaluated by applying it to image segmentation. The probabilistic atlas was found to be superior to the other shape models (P < 0.001) in this study.

Current-density estimation of exercise-induced ischemia in patients with multivessel coronary artery disease.

Magnetocardiographic and body surface potential mapping data measured in 6 patients with multivessel coronary artery disease were used in equivalent current-density estimation (CDE). Patient-specific boundary-element torso models were acquired from magnetic resonance images. Positron emission tomography data registrated with anatomical magnetic resonance imaging data provided the gold standard. Discrete current-density estimation values were computed on the epicardial surface of the left ventricle from difference (stress-rest) ST-segment maps. The ill-posed inverse problem was regularized with 3 different methods (Tikhonov regularization with an identity or a surface Laplacian operator and a maximum a posteriori estimator). Comparisons with positron emission tomography studies showed that the maximum a posteriori estimator is superior to other regularizations, provided that a suitable a priori information is available. In general, good correspondence was found for segments of high and low amplitude in current-density estimations, and the viable and scar areas in positron emission tomography, respectively.

Multimodality MR imaging assessment of myocardial viability: combination of first-pass and late contrast enhancement to wall motion dynamics and comparison with FDG PET-initial experience.

PURPOSE: To combine three magnetic resonance (MR) imaging modalities-dobutamine stress cine, first pass, and late contrast material-enhanced T1-weighted imaging-and to compare the results with 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in the assessment of unviable myocardium in coronary artery disease. MATERIALS AND METHODS: Ten patients with multivessel coronary artery disease underwent MR imaging before and 6 months after bypass surgery. Left ventricular cine MR imaging was performed at rest and during dobutamine infusion. Inversion-recovery gradient-echo images were obtained to study myocardial contrast enhancement at first pass and 5 minutes later. FDG PET was performed with orally administered acipimox before surgery. RESULTS: With dobutamine cine MR imaging, unviable myocardium was detected with a sensitivity of 79% and a specificity of 93%; postoperative wall thickening was the standard. First-pass analysis increased these values to 97% and 96%; analysis of late enhancement with T1-weighted imaging, to 62% and 98%. FDG PET had a sensitivity of 81% and a specificity of 86%. CONCLUSION: The combination of first-pass enhancement analysis and wall motion assessment with stress significantly increases the specificity of MR imaging in the detection of unviable sectors.

The effect of geometric and topologic differences in boundary element models on magnetocardiographic localization accuracy.

This study was performed to evaluate the changes in magnetocardiographic (MCG) source localization results when the geometry and the topology of the volume conductor model were altered. Boundary element volume conductor models of three patients were first constructed. These so-called reference torso models were then manipulated to mimic various sources of error in the measurement and analysis procedures. Next, equivalent current dipole localizations were calculated from simulated and measured multichannel MCG data. The localizations obtained with the reference models were regarded as the "gold standard." The effect of each modification was investigated by calculating three-dimensional distances from the gold standard localizations to the locations obtained with the modified model. The results show that the effect of the lungs and the intra-ventricular blood masses is significant for deep source locations and, therefore, the torso model should preferably contain internal inhomogeneities. However, superficial sources could be localized within a few millimeters even with nonindividual, so called standard torso models. In addition, the torso model should extend long enough in the pelvic region, and the positions of the lungs and the ventricles inside the model should be known in order to obtain accurate localizations.

Bioelectromagnetic localization of a pacing catheter in the heart.

The accuracy of localizing source currents within the human heart by non-invasive magneto- and electrocardiographic methods was investigated in 10 patients. A non-magnetic stimulation catheter inside the heart served as a reference current source. Biplane fluoroscopic imaging with lead ball markers was used to record the catheter position. Simultaneous multichannel magnetocardiographic (MCG) and body surface potential mapping (BSPM) recordings were performed during catheter pacing. Equivalent current dipole localizations were computed from MCG and BSPM data, employing standard and patient-specific boundary element torso models. Using individual models with the lungs included, the average MCG localization error was 7+/-3 mm, whereas the average BSPM localization error was 25+/-4 mm. In the simplified case of a single homogeneous standard torso model, an average error of 9+/-3 mm was obtained from MCG recordings. The MCG localization accuracies obtained in this study imply that the capability of multichannel MCG to locate dipolar sources is sufficient for clinical purposes, even without constructing individual torso models from x-ray or from magnetic resonance images.

Multislice MRI in assessment of myocardial perfusion in patients with single-vessel proximal left anterior descending coronary artery disease before and after revascularization.

BACKGROUND: Our purpose was to use multislice MRI for detection of reversible myocardial ischemia and assessment of the effect of revascularization on tissue perfusion in patients with coronary artery disease. METHODS AND RESULTS: Eleven patients with single-vessel proximal left anterior descending coronary artery disease were studied with MRI and thallium scintigraphy before and 3 months after revascularization. All patients had a reversible perfusion defect by scintigraphy before treatment. With a 1.5-T MR imager, IR-prepared turboflash images were acquired in three left ventricular short-axis planes during 0.05 mmol/kg Gd-DTPA bolus at rest and with dipyridamole-induced stress. Before treatment, stress increased enhancement slope in normal (6.4+/-4.4 to 7.4+/-5.0 s(-1), P<.04) and decreased it in underperfused (5.4+/-3.7 to 2.6+/-1.4 s(-1), P<.02) regions, resulting in a contrast-to-noise ratio of 6.87+/-3.09 in underperfused myocardium. Revascularization normalized enhancement patterns of the formerly underperfused myocardium and decreased defect size both in scintigraphy (66+/-53 degrees to 8+/-12 degrees, P<.001) and MRI sections (49+/-41 degrees to 9+/-8 degrees, P<.001). Agreement of 85% in detection and correlation of 0.86 (SEE, 21 degrees, P<.001) in sizing perfusion defects was found between MRI and scintigraphy. CONCLUSIONS: Multislice contrast-enhanced MRI can be used to detect myocardial perfusion defects in patients with coronary artery disease and in assessment of the effect of treatment on myocardial perfusion.

Alterations in T1 of normal and reperfused infarcted myocardium after Gd-BOPTA versus GD-DTPA on inversion recovery EPI.

This study tested whether Gd-BOPTA/Dimeg or Gd-DTPA exerts greater relaxation enhancement for blood and reperfused infarcted myocardium. Relaxivity of Gd-BOPTA is increased by weak binding to serum albumin. Thirty-six rats were subjected to reperfused infarction before contrast (doses = 0.05, 0.1, and 0.2 mmol/kg). delta R1 was repeatedly measured over 30 min. Gd-BOPTA caused greater delta R1 for blood and myocardium than did Gd-DTPA; clearance of both agents from normal- and infarcted myocardium was similar to blood clearance; plots of delta R1 myocardium/delta R1 blood showed equilibrium phase contrast distribution. Fractional contrast agent distribution volumes were approximately 0.24 for both agents in normal myocardium, 0.98 and 1.6 for Gd-DTPA and Gd-BOPTA, respectively, in reperfused infarction. The high value for Gd-BOPTPA was ascribed to greater relaxivity in infarction versus blood. It was concluded that Gd-BOPTA/Dimeg causes a greater delta R1 than Gd-DTPA in regions which contain serum albumin.

Assessment of right and left atrial function in patients with transplanted hearts with the use of magnetic resonance imaging.

BACKGROUND: The purpose of this study was to determine the volumes and cyclic volume changes of the cardiac atria after heart transplantation in physically healthy recipients. METHODS: Ten heart transplant recipients (New York Heart Association grade I) entered the protocol. All operations had been made with classic biatrial anastomoses. Eight healthy volunteers were studied as controls. To measure the volumes of both atria and left ventricular cavity, we used a gradient-echo cine sequence. The 10 mm slices covered both atria over the total cardiac cycle. Images were planimetered, and simultaneous volumes were totalled to give the cavity volume at each time phase. RESULTS: The heart rate of the heart transplant recipients was faster than in controls, which resulted in higher cardiac output. The atrial minimum volumes were significantly larger, and fractional emptying was smaller in transplanted hearts when compared with controls. Reservoir and stroke volumes were smaller and conduit volumes were larger in transplanted hearts than in controls. The atrial filling and emptying rates were lower in heart transplant recipients than in controls. CONCLUSIONS: The classic surgical technique used in heart transplantation results in large atria with decreased volume changes and filling rates even in physically healthy transplant recipients. Magnetic resonance imaging is a reliable tool in assessment of atrial volumes and cyclic function after heart transplantation.

Verapamil reduces the size of reperfused ischemically injured myocardium in hypertrophied rat hearts as assessed by magnetic resonance imaging.

Contrast-enhanced magnetic resonance (MR) imaging was used to detect and quantify the extent of myocardial injury after a brief coronary occlusion and reperfusion in response to verapamil treatment in a rat model of left ventricular hypertrophy (LVH). Two groups of rats were prepared by banding the abdominal aorta for 7 to 8 weeks to produce LVH. Group 1 (n = 13) received oral verapamil for 3 days, whereas group 2 (n = 13) received no therapy. Before MR examination was performed, each rat was subjected to 25 min of coronary artery occlusion followed by 1 hour of reperfusion. T1-weighted spin echo images were acquired before and after 0.3 mmol/kg gadoteridol was injected. Three images were acquired at contiguous levels of the LV and used to estimate the size of the myocardial injury. The size of the infarcted region was demarcated at postmortem examination by using triphenyltetrazolium chloride dye (TTC). Before contrast medium was administered, no significant difference in signal intensity was seen between nonischemic and reperfused ischemically injured myocardium. After gadoteridol was injected, a hyperintense zone indicative of myocardial injury was observed in 8 of 13 rats treated with verapamil and in all untreated animals. The size of the injury was significantly larger in untreated hearts than in hearts treated with verapamil as defined on MR images (25% +/- 5% vs 18% +/- 5%, p < 0.05) and TTC staining (12% +/- 4% and 4% +/- 1%, p < 0.05). Good correlation (r = 0.91) was found between the two measurements. No significant difference in the size of jeopardy area was seen between the two groups as (defined by blue dye infusion). In conclusion, contrast-enhanced MR imaging is a suitable technique to evaluate the effects of therapies applied to reduce myocardial injury. Verapamil can cause reduction in the extent of ischemic injury after reperfusion of hypertrophied myocardium.