Robert Amyot

Diagnosis of myocardial ischemia in hypertensive patients

Arterial hypertension can provoke a reduction in coronary flow reserve through several mechanisms that are not mutually exclusive (i.e. epicardial coronary artery disease (CAD), left ventricular hypertrophy and structural and/or functional microvascular disease). These different targets of arterial hypertension should be explored with different diagnostic markers. In fact, stress-induced wall motion abnormalities are highly specific for angiographically assessed epicardial CAD, whereas ST segment depression and/or myocardial perfusion abnormalities are frequently found with angiographically normal coronary arteries associated with left ventricular hypertrophy and/or microvascular disease. Exercise-electrocardiography stress test can be used to screen patients with negative maximal test due to its excellent negative predictive value, which is high and comparable in normotensives and hypertensives. When exercise-electrocardiography stress test is positive (or uninterpretable or ambiguous), an imaging stress-echo test is warranted for a reliable identification of significant, prognostically malignant epicardial CAD in view of an ischemia-guided revascularization.

Comparison between dipyridamole and adenosine as pharmacologic coronary vasodilators in detection of coronary artery disease with thallium 201 imaging

BackgroundBoth dipyridamole and adenosine are widely used as pharmacologic stressors with 201Tl imaging for detection of coronary artery disease. The purpose of this study was to compare dipyridamole and adenosine 201Tl imaging directly in patients with angiographically proved coronary artery disease.Methods and ResultsFifty-four patients were submitted to two planar 201Tl studies: one with dipyridamole and the other with adenosine. The interval between the two studies varied from 2 to 7 days and the order was assigned randomly. Three standard planar views were obtained 10 minutes and 4 hours after the injection of 3.0 mCi 201Tl. Administration of dipyridamole was as follows: 0.142 mg/kg/min during 4 minutes, followed by a slight exercise and 201Tl injection. The infusion of adenosine was as follows: 0.140 mg/kg/min during 6 minutes with injection of 201Tl after the third minute of infusion. Patients were asked to give their preference considering the number type, severity, and duration of side effects on a scale from 0 (worst) to 5 (best). Reading was done by two experienced observers. The heart was divided into three segments per view. The change in systolic blood pressure was-12±11 mm Hg for adenosine and-5±10 mm Hg for dipyridamole (p<0.001), and the change in heart rate was 18±10 beats/min for adenosine and 8±7 beats/min for dipyridamole (p<0.001). With regions of interest, ischemic/normal wall ratios were determined: 0.78 ± 0.06 for adenosine and 0.83±0.08 for dipyridamole (p<0.001). Adenosine detected 295 normal, 170 ischemic, and 21 scar segments, whereas dipyridamole detected 326, 135, and 25 segments, respectively. Patients preferred adenosine (4.3±1.0 for adenosine vs 3.8±1.5 for dipyridamole; p<0.04) mainly because of the short duration of side effects.ConclusionThis study shows that the use of adenosine with 201Tl imaging may have some advantages over dipyridamole.

Contrast echocardiography in Canada: Canadian Cardiovascular Society/Canadian Society of Echocardiography position paper

As an adjunct to transthoracic, transesophageal and stress echocardiography, contrast echocardiography (CE) improves the diagnostic accuracy of technically suboptimal studies when used in conjunction with harmonic imaging. Intravenous ultrasound contrast agents are indicated for left ventricular (LV) opacification and improvement of LV endocardial border delineation in patients with suboptimal acoustic windows. Demonstrated benefits of CE include improvement in the accuracy of LV measurements, regional wall motion assessment, evaluation of noncompaction cardiomyopathy, thrombus detection, Doppler signal enhancement and conjunctive use with stress echocardiography. Studies have shown the value of CE in the assessment and quantification of myocardial perfusion, and recent clinical trials have suggested a role for contrast perfusion imaging in the stratification of patients with suspected coronary artery disease. While it adds some time and cost to the echocardiographic study, CE frequently obviates the need for additional specialized, expensive and less accessible cardiac investigations, and allows for prompt and optimal subsequent patient management. Despite its proven advantages, CE is presently underused in Canada, and this situation will, unfortunately, not improve until several barriers to its use are overcome. Resolving these important hurdles is vital to the future of CE and to its eventual implementation into clinical practice of promising contrast-based diagnostic and therapeutic applications, including the assessment of perfusion by myocardial CE.

Effect of Coronary Bypass and Cardiac Valve Surgery on Systemic Endothelial Function

Seventeen patients scheduled for a cardiac procedure necessitating cardiopulmonary bypass underwent serial perioperative assessment of brachial artery flow-mediated dilation. Patients who underwent coronary bypass surgery had a sustained systemic endothelial dysfunction in the perioperative period, whereas those undergoing cardiac valve surgery experienced transient postoperative systemic endothelial dysfunction.

Effect of cardiac resynchronization therapy on regional left ventricular function: a speckle tracking strain analysis

AIMS The mechanisms associated with cardiac resynchronization therapy (CRT) benefits have been elucidated in part, however little is known about the effects of biventricular pacing (BVP) on regional myocardial contractility. METHODS AND RESULTS Twenty patients with conventional CRT criteria were studied before and after device implantation. Speckle tracking strain analysis was performed from standard bidimensional acquisitions during different pacing configurations. Longitudinal and transverse strains were measured for the six basal left ventricular (LV) segments. Acute CRT improved LV end-diastolic and end-systolic volumes without significantly modifying LV ejection fraction. Moreover, CRT produced significant changes in regional strain. When compared with spontaneous rhythm, simultaneous BVP caused a significant increase in longitudinal septal strain (-4.8 vs. -7.3%, P = 0.003) and a significant decrease in longitudinal lateral strain (-8.2 vs. -5.9%, P = 0.03). Simultaneous BVP also induced a significant decrease in transverse lateral strain from 17.9 to 10.9% (P = 0.004). CONCLUSION In this acute echocardiographic study, BVP decreased lateral wall deformation while improving septal wall contraction, thus potentially improving LV contractile pattern.

Assessment of a right ventricular metastasis using contrast echocardiography perfusion imaging

Cardiac metastases of thyroid carcinomas are rarely diagnosed ante mortem and infrequently reported in the literature. A 68-year-old man with known papillary thyroid carcinoma presented to the hospital with progressive shortness of breath. A transthoracic echocardiogram revealed a right ventricular mass. Contrast echocardiography perfusion imaging was used to evaluate the vascularity of the mass.

Echocardiographic evaluation of cardiac dyssynchrony

First described a decade ago, cardiac resynchronization therapy (CRT) has recently become a proven therapeutic strategy for refractory heart failure. Large clinical trials have shown a reduction in both morbidity and mortality in patients treated with CRT. Initial patient selection has relied mainly on electrocardiographic criteria, which allows identification of only 70% of responders. Accordingly, echocardiographic criteria were developed to identify mechanical dyssynchrony in an effort to improve patient selection. Multiple echocardiographic criteria have since been proposed, with no consensus as to which parameter better predicts CRT response. Although comparison studies using different criteria are underway, current evaluation of dyssynchrony should probably use an integrated multiparameter approach. The objective of the present article was to review the role of echocardiography in the evaluation of cardiac dyssynchrony in clinical practice.

Left ventricular ejection fraction assessment by non-cardiologists from transverse views using a simplified wall motion score index.

For the non-cardiologist emergency physician and intensivist, performing an accurate estimation of left ventricular ejection fraction (LVEF) is essential for the management of critically ill patients, such as patients presenting with shock, severe respiratory distress or chest pain. Our objective was to develop a semi-quantitative method to improve visual LVEF evaluation. A group of 12 sets of transthoracic echocardiograms with LVEF in the range of 18–64% were interpreted by 17 experienced observers (PRO) and 103 untrained observers or novices (NOV), without previous training in echocardiography. They were asked to assess LVEF by two different methods: i) visual estimation (VIS) by analysing the three classical left ventricle (LV) short-axis views (basal, midventricular and apical short-axis LV section) and ii) semi-quantitative evaluation (base, mid and apex (BMA)) of the same three short-axis views. The results for each of these two methods for both groups (PRO and NOV) were compared with LVEF obtained by radionuclide angiography. The semi-quantitative method (BMA) improved estimation of LVEF by PRO for moderate LV dysfunction (LVEF 30–49%) and normal LVEF. The visual estimate was better for lower LVEF (<30%). In the NOV group, the semi-quantitative method was better than than the visual one in the normal group and in half of the subjects in the moderate LV dysfunction (LVEF 30–49%) group. The visual estimate was better for the lower LVEF (ejection fraction <30%) group. In conclusion, semi-quantitative evaluation of LVEF gives an overall better assessment than VIS for PRO and untrained observers.

Ventricular septal rupture and right ventricular free wall dissection after inferior myocardial infarction: a case report and review of the literature.

Ventricular septal rupture (VSR) with dissection of the right ventricular free wall is an extremely rare complication after inferior myocardial infarction. Mortality is 100% without surgical treatment. The optimal surgical strategy remains unclear because of the limited number of cases, but repair of VSR alone might be equally effective as repair of VSR and right ventricular free wall reconstruction. Transesophageal echocardiography is an important adjunct to transthoracic echocardiography to establish the diagnosis.

Performance of a Simplified Wall Motion Score Index Method for Noncardiologists to Assess Left Ventricular Ejection Fraction

Backgrounds. For emergency physicians performing a goal-directed transthoracic echocardiogram (TTE), a reliable estimate of LVEF must be obtained rapidly. We compared rapid LVEF estimates obtained from short axis sections to those obtained from apical sections using two methods of evaluation. Methods. The TTEs of 6 patients were interpreted by 16 echo-proficient readers (PRO group) and 105 novice readers (NOV group). LVEF was assessed by each group. The strategies consisted of either a global visual estimation (VIS) of LVEF or semiquantitative (SQ) methods. Results. Using RNV and BIP as a reference standard, NOV readers performed better with the SQ method than global visual estimation. For NOV readers, best agreement was achieved with the 234C sequence in low LVEF situations, but with the BMA series in normal LVEF settings. Neither series of views was better than the other in the setting of mild LVEF depression. Conclusion. Semi-quantitative method was superior to global visual estimation of LVEF in NOV group in most of the LVEF ranges.