Assessment of myocardial perfusion by videodensitometry in the canine model

Assessment of the functional severity of coronary stenoses has become increasingly important as the intrinsic limitations of coronary angiography have been documented. Videodensitometric coronary flow reserve has been proposed as a means to assess the physiologic significance of a coronary stenosis in humans. This study compared videodensitometric assessment of coronary flow with microsphere quantitation in the closed chest canine model.In five dogs, flow rates were assessed at baseline, after vasodilation with adenosine, after vasoconstriction with vasopressin and during rapid cardiac pacing. The videodensitometric peak density, time to one-half peak density and washout time (time from peak to one-half peak density) were compared at each flow state with flow assessed by microsphere injection. Reproducibility of videodensitometric measurements from two different coronary injections during the same flow state was best with peak density (r = 0.94).Videodensitometric flow ratios (flow state under study to flow at rest) using peak density demonstrated a fair correlation with flow ratios by microsphere (r = 0.81). There was poor correlation between flow ratios when time to one-half peak or washout time was used.Videodensitometric flow measurements used in vivo to assess a wide range of drug-induced coronary flows may not accurately reflect coronary flow measured by microsphere

Doppler evaluation of patients with constrictive pericarditis: Use of tricuspid regurgitation velocity curves to determine enhanced ventricular interaction

AbstractObjectives. This study sought to examine the value of analyzing Doppler echocardiographically derived tricuspid regurgitation signals during respiration in relation to the diagnosis of constrictive pericarditis.Background. A physiologic hallmark of constrictive pericarditis is enhanced ventricular interdependence, which produces reciprocal changes in right and left ventricular filling and ejection dynamics during the respiratory cycle. It was hypothesized that these changes could be detected noninvasively by analyzing Doppler echocardiographically derived tricuspid regurgitation signals and that this information could assist in noninvasively diagnosing constrictive pericarditis.Methods. Simultaneous Doppler echocardiography and catheterization studies of the right and left sides of the heart with high fidelity pressure manometers were performed in 5 patients with surgically confirmed constrictive pericarditis and 12 patients (control subjects) with heart failure due to other causes.Results. Changes observed in tricuspid regurgitation Doppler echocardiographic variables from onset to peak inspiration in patients with constrictive pericarditis were significantly different from those in control subjects. Mean (±SD) percent change in maximal tricuspid regurgitation velocity was 13% ± 6% and −8% ± 7% in the constrictive pericarditis and control groups, respectively (p < 0.0001); mean percent change in tricupsid regurgitation signal duration was 18% ± 2% and −2% ± 7%, respectively (p < 0.0001); mean percent change in tricuspid regurgitation time velocity integral was 27% ± 15% and −10% ± 12%, respectively (p < 0.0001).Conclusions. Respiratory changes in Doppler echocardiographically derived tricuspid regurgitation peak velocity and velocity duration are increased in patients with constrictive pericarditis and may be helpful in diagnosing this condition noninvasively

Outcome of Patients With Hypertrophic Cardiomyopathy and a Normal Electrocardiogram

ObjectivesThis study sought to clarify the frequency, clinical phenotype, and prognosis of those patients with hypertrophic cardiomyopathy (HCM) who present with a normal electrocardiogram (ECG).BackgroundHypertrophic cardiomyopathy is the most common cause of sudden death in young people. Screening advocates have recommended a 12-lead ECG for the early detection of HCM in athletes, yet the clinical outcomes of those presenting with a normal ECG remains to be fully delineated.MethodsBaseline characteristic and echocardiographic data were collected on all patients with HCM who initially presented to our institution with a diagnostic echocardiogram but a normal ECG. Follow-up was obtained and compared with the prognosis of HCM patients who presented with abnormal ECGs.ResultsWe compared 135 HCM patients with a normal ECG with 2,350 HCM patients with an abnormal ECG. The latter group was more likely to have worse symptoms, have higher gradients, and a greater degree of septal wall thickness than the patients with a normal ECG. Severe obstructive symptoms requiring surgical myectomy and implantation of an implantable cardioverter-defibrillator were more common in patients with abnormal ECGs. Cardiac survival was significantly better in the group with a normal ECG at presentation—none of these patients had a cardiac death at follow-up.ConclusionsAlmost 6% of patients presenting with demonstrable echocardiographic evidence of HCM had a normal ECG at the time of diagnosis. This subset of patients with normal ECG-HCM appears to exhibit a less severe phenotype with better cardiovascular outcomes

Intravascular ultrasound imaging: In vitro validation and pathologic correlation

AbstractIntravascuiar ultrasound imaging is a new method in which high resolution images of the arterial wall are obtained with use of a catheter placed within an artery. An in vitro Plexiglas well model was used to validate measurements of the luminal area, and an excellent correlation was obtained. One hundred thirty segments of fresh peripheral arteries underwent ultrasound imaging and the findings were compared with the corresponding histopathologic sections. luminal areas determined with ultrasound imaging correlated well with those calculated from microscopic slides (r = 0.98).Three patterns were identified on the ultrasound images: 1) distinct interface between media and adventitia, 2) indistinct interface between media and adventitia but different echo density layers, and 3) diffuse homogeneous appearance. The types of patterns depended on the relative composition of the and adventitia. Calcification of intimal plaque obscured underlying structures. Atherosclerotic plaque was readily visualized but could not always be differentiated from the underlying media

Outcome of Mildly Symptomatic or Asymptomatic Obstructive Hypertrophic Cardiomyopathy A Long-Term Follow-Up Study

ObjectivesThe purpose of this study was to characterize the prognosis of minimally symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM).BackgroundRecent data have suggested that obstruction may be present in the majority of HCM patients, irrespective of cardiac symptoms. The prognosis of minimally symptomatic obstructive HCM remains poorly defined.MethodsWe examined 544 consecutive adult patients (age 59 ± 16 years; 55% men) with obstructive HCM documented by Doppler echocardiography who were free of severe cardiac symptoms, and we performed clinical follow-up (median 9.3 years).ResultsThere was only a slight excess mortality of the cohort in comparison to the expected survival of a similar U.S. general population (10-year observed vs. expected survival, 69.3% vs. 71.9%; p = 0.04) and 46% of the deaths were attributable to noncardiac causes. However, there was a clear relation between increasing severity of the left ventricular outflow tract (LVOT) gradient and outcome. For patients with high resting gradients (Doppler peak velocity >4 m/s), survival was significantly impaired (53% at 10 years; p = 0.001 vs. expected), and death or severe symptoms occurred in 68% of these patients within 10 years after the initial evaluation. Conversely, there was no impairment of long-term survival for patients with less-severe resting obstruction. Independent predictors of mortality in the entire cohort were age, prior stroke, and LVOT gradient severity.ConclusionsPatients with obstructive HCM and mild or no symptoms have only slight excess mortality. However, patients with markedly elevated resting LVOT gradients are at a high risk of heart failure and death. These findings may have important implications for therapy, including the timing of septal reduction therapy

Epicardial vasomotor responses to acetylcholine are not predicted by coronary atherosclerosis as assessed by intracoronary ultrasound

Objectives.The purpose of this study was to use intravascular ultrasound to determine the morphologic appearance of the coronary arteries, relating the absence, presence and extent of atherosclerosis to the response of the coronary arteries to acetylcholine infusion.Background.Endothelial function plays a major role in the pathophysiology of myocardial ischemia and angina pectoris. The response of the coronary arteries to selective infusion of acetylcholine has been used to examine endothelial function, with vasoconstriction occurring in the absence of intact endothelial function. Vasoconstriction to acetylcholine infusion in humans without overt coronary artery disease has been attributed to early atherosclerosis not detected by coronary angiography.Methods.Twenty-nine patients without overt coronary artery disease underwent selective coronary angiography and selective intracoronary infusion of increasing concentrations of acetylcholine (10−6, 10−5and 10−4mol/liter), followed by intravascular ultrasound imaging.Results.The response of the coronary arteries to acetylcholine infusion was not dependent on the absence or presence of atherosclerotic plaque, as detected by intravascular ultrasound. The percent change in epicardial coronary artery diameter during acetylcholine infusion versus baseline was −14 ± 28% (mean ± SD) in the seven patients with no visible atherosclerosis on intravascular ultrasound versus −9 ± 20% in the 22 patients with visible atherosclerosis on intravascular ultrasound (p = NS, confidence interval −14% to 25%). There was a greater vasoconstrictive response to acetylcholine infusion in patients with risk factors for coronary artery disease than in those without risk factors (p = 0.003).Conclusions.The vasoreactive response to acetylcholine is not necessarily dependent on ultrasound detection of the presence or absence of atherosclerosis

Dual-Chamber Pacing for Hypertrophic Cardiomyopathy: A Randomized, Double-Blind, Crossover Trial

AbstractObjectives. In a double-blind, randomized, crossover trial we sought to evaluate the effect of dual-chamber pacing in patients with severe symptoms of hypertrophic obstructive cardiomyopathy.Background. Recently, several cohort trials showed that implantation of a dual-chamber pacemaker in patients with severely symptomatic hypertrophic obstructive cardiomyopathy can relieve symptoms and decrease the severity of the left ventricular outflow tract gradient. However, the outcome of dual-chamber pacing has not been compared with that of standard therapy in a randomized, double-blind trial.Methods. Twenty-one patients with severely symptomatic hypertrophic obstructive cardiomyopathy were entered into this trial after baseline studies consisting of Minnesota quality-of-life assessment, two-dimensional and Doppler echocardiography and cardiopulmonary exercise tests. Nineteen patients completed the protocol and underwent double-blind randomization to either DDD pacing for 3 months followed by backup AAI pacing for 3 months, or the same study arms in reverse order.Results. Left ventricular outflow tract gradient decreased significantly to 55 ± 38 mm Hg after DDD pacing compared with the baseline gradient of 76 ± 61 mm Hg (p < 0.05) and the gradient of 83 ± 59 mm Hg after AAI pacing (p < 0.05). Quality-of-life score and exercise duration were significantly improved from the baseline state after the DDD arm but were not significantly different between the DDD arm and the backup AAI arm. Peak oxygen consumption did not significantly differ among the three periods. Overall, 63% of patients had symptomatic improvement during the DDD arm, but 42% also had symptomatic improvement during the AAI backup arm. In addition, 31% had no change and 5% had deterioration of symptoms during the DDD pacing arm.Conclusions. Dual-chamber pacing may relieve symptoms and decrease gradient in patients with hypertrophic obstructive cardiomyopathy. In some patients, however, symptoms do not change or even become worse with dual-chamber pacing. Subjective symptomatic improvement can also occur from implantation of the pacemaker without its hemodynamic benefit, suggesting the role of a placebo effect. Long-term follow-up of a large number of patients in randomized trials is necessary before dual-chamber pacing can be recommended for all patients with severely symptomatic hypertrophic obstructive cardiomyopathy.(J Am Coll Cardiol 1997;29:435–41