Sammy Y. Chan

Does a hypertonic saline load predict fluid retention in pacing induced heart failure

OBJECTIVEnWe examined the response to hypertonic saline challenge (SC) as a potential predictor of fluid retention during heart failure induced by rapid ventricular pacing.nnnMETHODSnTwelve dogs (22 +/- 4 kg) were given an intra-arterial bolus of 30 ml of 20% saline after establishing baseline fluid intake and urine output (24 h). Dogs were classified according to whether they drank more (Group A) or less (Group B) than the amount required to dilute the s.c. to isotonicity. Fluid retention was then assessed during heart failure after rapid ventricular pacing according to a graded ordinal scale and correlated with the responses to s.c..nnnRESULTSnNo difference was noted in baseline fluid intake (1112 +/- 236 ml in Group A vs. 809 +/- 129 ml in Group B). Five hours after s.c. cumulative water intake was significantly greater in Group A than in Group B (1018 +/- 136 vs. 591 +/- 17 ml) (P < 0.01). Urine sodium concentration was 113 +/- 11 and 124 +/- 28 mmol/l at baseline in Group A and B, respectively; increased to 190 +/- 21 and 295 +/- 59 mmol/l at 5 h and remained elevated 24 h after s.c., 177 +/- 60 and 274 +/- 55 mmol/l (both P < 0.01 for within-group comparisons vs. baseline). Urine sodium concentration was less in Group A than in Group B at 5 and 24 h (P < 0.05). The fluid retention score was greater in Group A (3.6 +/- 0.5) than in Group B (0.8 +/- 0.4) (P < 0.01). Fluid retention in heart failure correlated with water intake after the pre-pacing s.c. (r = 0.68, P < 0.025) and inversely with urine concentrating ability (r = -0.58, P < 0.05). Furthermore, water intake and urine concentrating ability following the s.c. were inversely related (r = -0.67, P < 0.02).nnnCONCLUSIONSnWe conclude that normal dogs may be classified according to their fluid intake after s.c.. Those dogs that drank excessively and produced a dilute urine were more likely to retain fluid during pacing-induced heart failure. Hence, fluid intake and the ability to excrete a concentrated urine after a saline challenge may be useful variables to predict fluid retention in pacing-induced heart failure.

Novel methodology for echocardiographic quantification of cardiac shape

BACKGROUNDnLeft ventricular (LV) shape is a major determinant of cardiac physiology with important prognostic implications. Current techniques are limited in their ability to characterize shape. Regional curvature analysis is a recently developed method that is free of idealized shape assumptions and is applicable globally or regionally.nnnOBJECTIVEnTo measure the change in regional curvature from diastole to systole to determine whether modifications of this methodology can be applied to study LV shape noninvasively, and to compare this method with other shape analysis methods.nnnANIMALSnSeventeen normal dogs underwent transthoracic echocardiography. LV dimensions were measured at end-diastole and end-systole. LV endocardial outlines were traced from apical four-chamber views. LV short to long axis (D/L) ratios and eccentricity index (E) were calculated. Regional curvatures were determined using customized software. Reproducibility of regional curvature was also determined.nnnMAIN RESULTSnLV regional curvature values were consistent among animals at diastole and systole in all areas. Regional curvature showed divergence in different areas. D/L ratios showed a 7% decrease from diastole to systole, whereas E demonstrated a 10% increase. However, regional curvature exhibited a 39% change, suggesting that this methodology is more sensitive. Duplicate curvature values from same or different cardiac cycles were highly reproducible.nnnCONCLUSIONSnQuantitative regional curvature analysis can be applied with echocardiography to study LV shape. This methodology is more sensitive than current methods, is reproducible and may be applicable to the noninvasive study of shape changes in cardiac disease.

COMPARISON OF PSYCHOSOCIAL QUESTIONNAIRES BETWEEN SPONTANEOUS CORONARY ARTERY DISSECTION (SCAD) AND NON-SCAD POPULATIONS UNDERGOING CARDIAC REHABILITATION PROGRAM AFTER MYOCARDIAL INFARCTION

Spontaneous coronary artery dissection (SCAD) is an infrequent but important cause of myocardial infarction (MI) in women. We previously reported that emotional stressors were important precipitants for SCAD. We sought to compare the psychosocial profile of patients with SCAD and standard coronary

Cardiac positron emission tomography: the foundations and clinical applications.

Cardiac PET studies may have a role in the early detection of coronary artery disease. The early prediction of the ultimate fate of reperfused myocardium with cardiac PET imaging remains elusive. At present the predominant clinical use of PET scans lies in the identification of ischemic but viable tissue. Cardiac PET imaging with a combination of perfusion and metabolic tracers can distinguish those patients with a history of previous infarctions and severe heart failure who will benefit from therapeutic revascularization. Conversely, the group that is not expected to improve will be spared needless and risky attempts at revascularization and will become candidates for cardiac transplantation at an earlier stage.

The Impact of Reduced Cardiac Rehabilitation on Maximal Treadmill Exercise Time: A RANDOMIZED CONTROLLED TRIAL

Purpose: Cardiac rehabilitation programs (CRPs) remain underutilized partly because of access barriers. We therefore evaluated a CRP with fewer center-based sessions (rCRP) compared with standard CRP (sCRP) with respect to changes in exercise capacity and cardiac risk factors. Methods: In this randomized controlled noninferiority trial, primary and secondary prevention patients at low and moderate risk were randomized to an sCRP (n = 60) or an rCRP (n = 61). Over 4 months, sCRP and rCRP participants attended 32 and 10 on-site cardiac rehabilitation sessions, respectively. The primary outcome was the difference in the change in exercise capacity from baseline at 4 and 16 months between the groups measured in seconds from a maximal treadmill exercise test. Noninferiority of the rCRP was tested with mixed-effects model analysis with a cut point of 60 seconds for the upper value of the group estimate. Results: Attendance was higher for the rCRP group (97% ± 63% vs 71% ± 22%, P = .002). Over 16 months, exercise test time increased for the sCRP (524 ± 168 to 604 ± 172 seconds, P < .01) and the rCRP (565 ± 183 to 640 ± 192 seconds, P < .01). The rCRP was not inferior to the sCRP regarding changes in treadmill time (48.47 seconds, P = .454). The rCRP was not inferior to the sCRP regarding metabolic and anthropometric risk factors. Conclusion: Our findings suggest that, for a selected group of low-/moderate-risk patients, the number of center-based CRP exercise sessions can be decreased while maintaining reduced cardiovascular risk factors.

Prevalence and Associated Clinical Characteristics of Exercise-Induced ST-Segment Elevation in Lead aVR

Background Exercise-induced ST-segment elevation (STE) in lead aVR may be an important indicator of prognostically important coronary artery disease (CAD). However, the prevalence and associated clinical features of exercise-induced STE in lead aVR among consecutive patients referred for exercise stress electrocardiography (ExECG) is unknown. Methods All consecutive patients receiving a Bruce protocol ExECG for the diagnosis of CAD at a tertiary care academic center were included over a two-year period. Clinical characteristics, including results of coronary angiography, were compared between patients with and without exercise-induced STE in lead aVR. Results Among 2227 patients undergoing ExECG, exercise-induced STE ≥1.0mm in lead aVR occurred in 3.4% of patients. Patients with STE in lead aVR had significantly lower Duke Treadmill Scores (DTS) (-0.5 vs. 7.0, p<0.01) and a higher frequency of positive test results (60.2% vs. 7.3%, p<0.01). Furthermore, patients with STE in lead aVR were more likely to undergo subsequent cardiac catheterization than those without STE in lead aVR (p<0.01, odds ratio = 4.2). Conclusions Among patients referred for ExECG for suspected CAD, exercise-induced STE in lead aVR was associated with a higher risk DTS, an increased likelihood of a positive ExECG, and referral for subsequent coronary angiography. These results suggest that exercise-induced STE in lead aVR may represent a useful ECG feature among patients undergoing ExECG in the risk stratification of patients.