Influence of heart rate reduction on Doppler myocardial imaging parameters in a small animal model.

In small animals studies, sick animals often have a significant reduction in heart rate while under anesthesia. The influence of heart rate reduction on Doppler myocardial imaging (DMI) parameters is not known. The aim of the present study was to assess the effect of heart rate reduction on DMI parameters in a small animal model. Twenty-four rats underwent transthoracic echocardiography at baseline and during the administration of ivabradine IV. In all rats, left ventricular (LV) systolic velocity, strain and strain rate were measured in the anteroseptal and inferolateral wall segments from short axis views. In 12 rats (group A), M-mode analysis was also performed for assessment of global LV function. In the other 12 rats (groups B), contractility was quantified invasively using the end-systolic pressure-volume relation (ESPVR) and the preload recruitable stroke work (PRSW). During ivabradine, administration heart rate decreased by 18% in group A (p < 0.001) and 36% in group B (p < 0.001). There was a slight increase in LVEDD and LVESD, with no change in cardiac output or LV ejection fraction. During ivabradine administration, DMI parameters did not change significantly in any group. No significant correlation between DMI parameters and heart rate (r(2) = 0.05) or ejection time (r(2) = 0.14) could be found. The absence of changes in contractility was confirmed by the absence of change in PRSW and end-systolic elastance (Ees). In conclusion, moderate heart rate reduction did not influence DMI measurements in this specific rat model. Therefore, in the interpretation of DMI data when performing small animal studies, moderate heart rate reduction does not need to be taken into account.

Abnormal response to inotropic stimulation in young asymptomatic type I diabetic patients demonstrated by serial gated myocardial perfusion SPECT imaging.

PURPOSE: In subjects without underlying cardiac disease dobutamine is known to enhance systolic LV function and LV relaxation. As end-systolic (ES) and end-diastolic (ED) volumes (V) can be derived from gated SPECT we intent to study these volumes and their response to dobutamine in order to have a better understanding of the mechanism by which stroke volume (SV) increases during dobutamine infusion. We intent to do this in normal controls and in young diabetic subjects. METHODS: After injection of sestamibi, serial gated SPECT were obtained at baseline, and during low doses of dobutamine infusion in 12 asymptomatic type I diabetic patients, and in 12 age matched controls. LV EDV, ESV, SV and EF were calculated with the QGS program. RESULTS: Gated SPECT showed comparable LV EF and SV in both groups at rest. There was a significant increase in LVEF and SV during dobutamine infusion but in the diabetic patients the increase in SV was due to a decrease in ESV from 25+/-5 to 20+/-6 ml/m2 (p=0.002) and no change in EDV. In normal controls, the increase in EF was due to an increase in EDV from 69+/-10 to 73+/-12 ml/m2 (p=0.002) with no significant change in ESV. CONCLUSION: These data confirm the presence of subclinical abnormalities of diastolic function in asymptomatic type I diabetic patients and show differences in adaptation to inotropic stimulation in order to preserve the increase in stroke volume and LV ejection fraction.

Contrast harmonic imaging improves the evaluation of left ventricular function in ventilated patients: comparison with transesophageal echocardiography.

AIMS: The study examined the value of contrast echocardiography (CE) in the assessment of left ventricular (LV) wall motion in ventilated patients in comparison with transesophageal (TOE) and standard fundamental transthoracic imaging (SE). METHODS: Transthoracic echocardiograms were done in 40 ventilated patients. Wall motion was evaluated using the recommendations of the American Society of Echocardiography on SE, CE and TOE. A visualization score was assigned on a scale of 2-0 for each of 16 segments. The segment was assigned a value of 2 if the segment was seen in both systole and diastole, 1 if seen only in systole or diastole, and 0 if not seen at all. A confidence score was also given for each segment with each technique (unable to evaluate; not sure; sure). The ejection fraction (EF) was estimated visually for each technique, and a confidence score was also applied to the EF. RESULTS: Visualization score 0 was present in 6.2 segments/patient on SE, 1.2 on CE (P<0.0001) and 1.1 on TOE (P<0.0001). An average of 6.5 segments were read with surety on SE, 11.5 on CE (P<0.0001) and 12.3 on TOE ( P<0.0001 ). There was no significant difference for CE vs TOE. EF was uninterpretable in 32% on SE, 0% on CE (P<0.001 and 0% on TOE (P<0.001). The EF was read with surety in 53% of patients on SE, 88% on CE (P < 0.0001) and 93% with TOE (P<0.0001) with no difference for CE vs TOE. Thus, wall motion was seen with more confidence on CE and TOE. CONCLUSIONS: In the ventilated patients with suboptimal transthoracic echocardiograms for the evaluation of the LV function, CE provides image quality of regional and global LV function similar to that achieved with TOE echocardiography.

Aortic dissection and Turner's syndrome.

Cardiovascular malformations, especially coarctation of the aorta and bicuspid aortic valve, are common in patients with Turner's syndrome. Only 46 patients with aortic dissection and/or rupture have been described. All patients had associated aortic dilation or aneurysm. In all cases except three, involvement of the ascending aorta was present, making surgery often imperative. We describe a rare case of a DeBakey type IIIb aortic dissection (without involvement of the proximal aorta) in a patient with Turner's syndrome mosaicism. The dissection occurred two weeks after a caesarean section because of eclampsia. No aortic dilation or other cardiovascular malformations were found. The distal extension and uncomplicated nature of the dissection indicated medical management. After fifteen months of follow-up, she is clinically doing well and repeated CT scan shows a stable dissection of the descending and abdominal aorta without dilation.

Rapid gastric emptying of a liquid meal in long-term Type 2 diabetes mellitus.

Both delayed and accelerated gastric emptying rate (GER) have been reported in patients with diabetes mellitus. Delayed GER has been attributed to autonomic neuropathy in established diabetes but rapid GER was demonstrated in early Type 2 diabetes. The aim of the study was to investigate rapid gastric emptying in a group of people with long-duration Type 2 diabetes. GER of a radiolabelled liquid meal was studied scintigraphically in 20 Type 2 patients with a mean (+/-SEM) duration of diabetes 13 (+/-1) years. The 50% emptying time (t50) for the liquid meal was shorter in diabetic patients (29.6+/-2.1 min) than in controls (39.2+/-1.9 min; p<0.0005). Accelerated emptying (t50 value below the shortest t50 of controls) was evidenced in 14/20 patients and delayed emptying (t50 value exceeding the upper t50 of controls) in none. Patients with accelerated GER were comparable for BMI, diabetes duration, HbA1c and fasting glycaemia to those with normal GER. Rapid GER for liquids was found in the presence or absence of autonomic neuropathy. Seven of the patients with rapid emptying of the liquid meal were reassessed using a solid meal. Only one patient demonstrated rapid emptying of the solid meal, which was normal in 3 and delayed in 3 patients. In conclusion, accelerated GER can be found in long-term Type 2 diabetes but there is no concordance between GER of a liquid and a solid meal.