Imran Afridi

Dobutamine Echocardiography in Myocardial Hibernation Optimal Dose and Accuracy in Predicting Recovery of Ventricular Function After Coronary Angioplasty

BACKGROUNDnMyocardial hibernation is a condition of chronic left ventricular dysfunction associated with severe coronary artery disease whereby significant recovery of function occurs after revascularization. Identification of hibernating myocardium has important prognostic and therapeutic implications. The presence of contractile reserve as assessed by dobutamine echocardiography may be promising in the detection of hibernation. We designed a prospective study to evaluate the accuracy and optimal dose of dobutamine echocardiography for predicting recovery of ventricular function after angioplasty in patients with stable coronary artery disease and ventricular dysfunction.nnnMETHODS AND RESULTSnTwenty patients with stable coronary artery disease and segmental ventricular dysfunction scheduled for coronary angioplasty underwent dobutamine echocardiography before revascularization using incremental doses of 2.5, 5, 7.5, 10, 20, 30, and 40 micrograms/kg per minute every 3 minutes. Digital images of all eight stages were displayed simultaneously (two quad screens side by side) and interpreted using a 16-segment ventricular model and a 6-grade scoring system. Serial resting echocardiograms before, early (< 1 week), and late (> or = 6 weeks) after angioplasty were digitized and randomized in a quad-screen format for the assessment of recovery of function. Wall motion score index in the revascularized regions decreased from 2.86 +/- 0.76 before angioplasty to 2.12 +/- 1.03 late after angioplasty (P < .05). Of 320 ventricular segments, 148 had abnormal wall motion at baseline and 114 were revascularized. Recovery of function (> or = 2 grades) occurred in 25% of revascularized segments early and in 33% late after angioplasty. Of the 34 abnormal segments not revascularized, recovery of function occurred in only 1. During dobutamine echocardiography, abnormal segments exhibited one of four responses: biphasic (improvement at low dose and worsening at high dose) in 28% of segments, sustained improvement (persistent improvement till peak dose) in 18%, worsening in 15%, and no change in 39%. A biphasic response had the highest predictive value (72%) for recovery of function followed by worsening only (35%), while the lowest was seen with a no-change or sustained improvement response (13% and 15%). Combining biphasic and worsening responses resulted in a sensitivity of 74% and specificity of 73% for assessment of recovery of individual segments and 90% and 60%, respectively, for functional recovery of individual patients (n = 10). In segments with a biphasic response, the low dose at which improvement in wall motion was most prevalent (84%) was 7.5 micrograms/kg per minute and increased to 94% when the 5 and 7.5 micrograms/kg per minute doses were displayed. The reworsening phase of the biphasic response was usually seen with doses > or = 20 micrograms/kg per minute but was also observed as early as the 7.5 micrograms/kg per minute dose.nnnCONCLUSIONSnThe wall motion response during dobutamine echocardiography is useful in the prediction of recovery of ventricular function after revascularization in patients with stable coronary artery disease and ventricular dysfunction. The administration of low as well as high doses of dobutamine is needed for optimal evaluation.

Dobutamine Echocardiography and Quantitative Rest-Redistribution 201Tl Tomography in Myocardial Hibernation Relation of Contractile Reserve to 201Tl Uptake and Comparative Prediction of Recovery of Function

BACKGROUNDnThe purposes of this study were to evaluate the comparative accuracy of dobutamine echocardiography and quantitative rest-redistribution 201Tl tomography in the prediction of recovery of function after revascularization and to assess the relation of contractile reserve to thallium uptake.nnnMETHODS AND RESULTSnThirty-four patients with stable coronary disease and regional dysfunction underwent dobutamine echocardiography (2.5 up to 40 micrograms.kg-1.min-1) and rest-redistribution 201Tl tomography 1 day before revascularization. Resting echocardiography and scintigraphy were repeated at > or = 6 weeks. Before revascularization, resting 201Tl uptake was similar in segments demonstrating biphasic or sustained improvement and was higher than in those exhibiting no change or worsening function during dobutamine. After revascularization, 201Tl uptake increased only in segments that showed a biphasic response (from 66 +/- 12% to 78 +/- 13%; P < .05). Biphasic response had a sensitivity of 74% and specificity of 89% for prediction of recovery. The use of biphasic or sustained improvement responses increased the sensitivity to 86% with a decrease in specificity to 68%. Qualitative thallium assessment provided a high sensitivity (98%) but poor specificity (27%). Quantification of thallium uptake, however, improved its accuracy: a maximal uptake (at rest or redistribution) of > or = 60% yielded a 90% sensitivity and a 56% specificity.nnnCONCLUSIONSnIn patients with myocardial hibernation, biphasic response during dobutamine is less sensitive but more specific for recovery of function, whereas indexes of 201Tl scintigraphy are in general more sensitive and less specific, the least accurate being a qualitative assessment of thallium uptake. The sensitivity and specificity of both methods, however, can be altered depending on the quantitative criteria of thallium uptake or combination of responses of the myocardium to dobutamine.

Assessment of Myocardial Viability With 99mTc Sestamibi in Patients Undergoing Cardiac Transplantation A Scintigraphic/Pathological Study

BACKGROUNDn99mTc sestamibi and 201 Tl are tracers that allow equivalent detection of myocardial infarction. However, because sestamibi does not undergo as much time-dependent redistribution as does 201Tl, it has been considered suboptimal for the detection of myocardial viability.nnnMETHODS AND RESULTSnFifteen consecutive patients with ischemic cardiomyopathy who underwent orthotopic cardiac transplantation received an intravenous injection of 99mTc sestamibi at 1 to 6 hours before transplantation. Rotational tomography of the excised, intact, native hearts was performed to quantify the extent of myocardial hypoperfusion. The hearts were then sliced and reimaged on a gamma camera, followed by pathological quantification of the extent and severity of scarred and normal myocardium. Samples of normally and abnormally perfused myocardium underwent gamma well counting to determine tissue radioactivity and were examined under light microscopy for delineation of myocardial structure after trichrome staining. The mean extent of scintigraphic scar quantified through the use of rotational tomography was 45 +/- 14% of the left ventricle and correlated closely with pathological scar size (r = .89), despite a slight overestimation. Scintigraphic scar size determined with planar imaging of the individual myocardial slices also correlated closely with pathological scar size (r = .88). A good correlation existed between tissue 99mTc sestamibi activity determined through well counting and histological evidence of myocardial viability (r = .89). Most hypokinetic and 40% of akinetic/dyskinetic myocardial segments contained scintigraphically and histologically normal myocardium.nnnCONCLUSIONSn99mTc sestamibi scintigraphy can be used to accurately quantify the extent of myocardial scarring. Furthermore, the relative sestamibi activity in perfusion defects, measured several hours after administration, is a good indicator of myocardial viability determined with microscopy.

Transesophageal echocardiography in critically ill patients: Feasibility, safety, and impact on management

Transesophageal echocardiography (TEE) is being used with increasing frequency in critically ill patients in whom transthoracic echocardiography (TTE) is often unsatisfactory in providing much needed information. We reviewed the indications, feasibility, and clinical impact of TEE in the intensive care setting at our institution. TEE was performed in 77 critically ill patients (age range 19 to 83 years) in whom TTE was inadequate or inconclusive. The general indications for performing a TEE were as follows: Hemodynamic instability (41%), possible endocarditis (34%), possible embolic source (21%), and possible aortic dissection (4%). In the subset of patients with hemodynamic instability, severe native mitral regurgitation was the most common underlying cause (25%), followed by hypovolemia after cardiac surgery (22%). TEE was feasible in all patients, 47% of whom were on mechanical ventilation. Two patients required stabilization before TEE, including a femoral artery-to-vein bypass in a patient with shock from a prosthetic valve obstruction. Complications, none of which proved to be fatal, occurred in two. Echocardiography led to a significant change in patient management in 46 of the 77 patients (60%), of which 48% was due solely to TEE. In these patients (n = 37), the TEE findings led to a change in medical management in 19% and to surgical intervention in 29%. While TTE remains the first line of diagnostic ultrasound and Doppler in critically ill patients, it can be technically difficult or inconclusive. In this setting, TEE provides a safe and powerful diagnostic tool that can help guide patient management.

Pseudoaneurysms of the mitral—aortic intervalvular fibrosa: Dynamic characterization using transesophageal echocardiographic and Doppler techniques

OBJECTIVESnThe aim of this study was to provide a detailed description of echocardiographic and Doppler features of pseudoaneurysms involving the mitral-aortic intervalvular fibrosa and to compare echocardiographic and aortographic findings.nnnBACKGROUNDnInfection of the aortic valve may spread to the aortic annulus, resulting in ring abscesses or pseudoaneurysms, or both, of the intervalvular fibrosa, which can alter patient management and prognosis.nnnMETHODSnThe echocardiographic and Doppler findings of 20 patients with pseudoaneurysms or ring abscesses, or both, were reviewed and compared with surgical and aortographic results.nnnRESULTSnA total of 23 lesions were identified, of which 16 were intervalvular pseudoaneurysms, and 7 were ring abscesses. Transthoracic echocardiography detected 43% of the lesions, whereas transesophageal echocardiography identified 90% (p < 0.01). The most distinct feature of the pseudoaneurysms was marked pulsatility, with systolic expansion and diastolic collapse (mean systolic area [+/- SD] 4.1 +/- 3.4 cm2 vs. diastolic mean area 1.8 +/- 2.2 cm2, p < 0.05). Using color Doppler, two types were identified: unruptured pseudoaneurysms (n = 9), which communicated only with the left ventricular outflow tract and had a distinct flow pattern, and ruptured pseudoaneurysms (n = 7), which, in addition, communicated with the left atrium or aorta. Compared with pseudoaneurysms, ring abscesses were smaller and nonpulsatile and showed either no flow or continuous systolic and diastolic flow, the site of paravalvular aortic insufficiency. In 10 patients who underwent aortography, three lesions were identified, and findings were concordant with echocardiography. However, in seven patients aortographic findings were normal, whereas echocardiography identified intervalvular pseudoaneurysms, all of which were documented at operation.nnnCONCLUSIONSnIntervalvular pseudoaneurysms are more frequently detected by transesophageal echocardiography than by aortography or transthoracic examination and exhibit distinct dynamic features and Doppler patterns that can further help characterize cavitary lesions in the aortic root and guide appropriate surgical intervention.

Serial Changes in Response of Hibernating Myocardium to Inotropic Stimulation After Revascularization: A Dobutamine Echocardiographic Study

OBJECTIVESnWe sought to evaluate the serial changes in the response of the hibernating myocardium to dobutamine stimulation after revascularization.nnnBACKGROUNDnAn improvement in myocardial contraction during dobutamine stress echocardiography (DSE), particularly a biphasic response, predicts recovery of rest function. However, little is known about the changes in the response of the myocardium to dobutamine after revascularization.nnnMETHODSnThirty-four patients with stable coronary artery disease and regional left ventricular dysfunction underwent DSE before, early (within 1 week) and late (>6 weeks) after coronary angioplasty. Dobutamine was given in incremental doses from 2.5 to 40 microg/kg body weight per min.nnnRESULTSnOf 180 revascularized segments with severe rest dysfunction, recovery of rest function was seen in 56 segments (31%) late after angioplasty, 80% of which had early recovery. Ventricular function during DSE was similar early and late after revascularization. Patients who showed a biphasic response to DSE before revascularization (n = 12) had the most improvement in function at rest (mean [+/-SD] wall motion score index [WMSI] 1.98 +/- 0.75 vs. 1.35 +/- 0.54, p < 0.05) and during DSE (2.11 +/- 0.67 vs. 1.21 +/- 0.41, p < 0.05) late after revascularization. Patients with sustained improvement during DSE before revascularization had no significant change in wall motion during DSE after angioplasty. However, patients without improvement in function at low dose DSE, who demonstrated worsening of function at a high dose, had significant augmentation in wall motion during DSE after revascularization (WMSI 2.16 +/- 0.50 vs. 1.60 +/- 0.57, p < 0.05). Patients who had no recovery of rest function had significant improvement in wall motion response to DSE, particularly when ischemia was inducible before revascularization.nnnCONCLUSIONSnIn myocardial hibernation, the majority of recovery of rest function occurs early after revascularization. Although patients who recover rest function show the most marked improvement in wall motion during DSE, those without recovery of rest function also have improved function during DSE, particularly when there is evidence of ischemia before revascularization.

722-6 Prediction of Recovery of Function of Hibernating Myocardium After Coronary Angioplasty: Comparison of Dobutamine Echocardiography and Rest-Redistribution Thallium Tomography

Dobutamine echocardiography (DE) and rest-redistribution Thallium-201 (TI) scintigraphy are promising techniques in the evaluation of myocardial hibernation. To assess the comparative accuracy of both modalities in the prediction of recovery of function following revascularization, 14 patients with chronic stable coronary artery disease and regional dysfunction underwent DE, rest and 4h redistribution TI tomography prior to, and late 16-8 wks) following coronaryangioplasty. Low and high dobutamine doses were used (2.5 up to 40xa0μg/kg/min). A 13 segment-LV model was used for analysis of both, quantitative TI tomograms and semiquantitative wall motion score (6 grades; hyperkinesiaxa0=xa00 to dyskinesiaxa0=xa05). Serial resting echocardiograms were digitized and randomized on a quad-screen. Of 182 segments, 91 had abnormal wall motion of which 54 were revascularized. Seventeen of the 54 revascularized segments (31%) exhibited significant recovery of function (xa0≥xa02 grade improvement) at late follow-up. In contrast, of the 37 dysfunctional segments not revascularized, none had improvement in function. In these unrevascularized dysfunctional segments, resting TI uptake was unchanged from preto late post angioplasty (68% vs 63%, Pxa0=xa0NS). However, in revascularized segments, a significant improvement in TI uptake was observed, the most pronounced being in segments showing recovery of function (72% to 89%, Pxa0=xa00.0002, nxa0=xa017). Criteria for prediction of recovery of function were, for DE, the presence of biphasic response (augmentation at low dose and worsening at peak dose) and for TI, a resting uptakexa0≥xa060% or an increase toxa0≥xa060% upon redistribution). The sensitivity for prediction of recovery of function of individual segments was 94% for DE and 100% for TI tomography with a specificity of 84% for DE and 53% for TI. In false positive segments by TI (nxa0=xa018), resting uptake was unchanged after angioplasty (78% vs 83%, Pxa0=xa0NS). Analysis by patients showed similar findings: both DE and TI tomography were 100% sensitive with a specificity of 78% and 63%, respectively. Dobutamine echocardiography and rest-redistribution TI tomography are therefore helpful in the assessment of myocardial hibernation. While both tests have similar sensitivity, dobutamine echocardiography appears to have a higher specificity for predicting significant recovery of systolic function following revascularization.