Gerald Maurer

“overestimation” of catheter gradients by doppler ultrasound in patients with aortic stenosis: a predictable manifestation of pressure recovery

OBJECTIVESnThis study sought to evaluate whether pressure recovery can cause significant differences between Doppler and catheter gradients in patients with aortic stenosis, and whether these differences can be predicted by Doppler echocardiography.nnnBACKGROUNDnPressure recovery has been shown to be a source of discrepancy between Doppler and catheter gradients across aortic stenoses in vitro. However, the clinical relevance of this phenomenon for the Doppler assessment of aortic stenosis has not been evaluated in patients.nnnMETHODSnTwenty-three patients with various degrees of aortic stenosis were studied with Doppler echocardiography and catheter technique within 24 h. Using an equation previously validated in vitro, pressure recovery was estimated from peak transvalvular velocity, aortic valve area and cross-sectional area of the ascending aorta and compared with the observed differences between Doppler and catheter gradients. Doppler gradients were also corrected by subtracting the predicted pressure recovery and then were compared with the observed catheter gradients.nnnRESULTSnPredicted differences between Doppler and catheter gradients due to pressure recovery ranged from 5 to 82 mm Hg (mean +/- SD, 19 +/- 16 mm Hg) and 3 to 54 mm Hg (12 +/- 11 mm Hg) for peak and mean gradients, respectively. They compared well with the observed Doppler-catheter gradient differences, ranging from -5 to 75 mm Hg (18 +/- 18 mm Hg) and -7 to 48 mm Hg (11 +/- 13 mm Hg). Good correlation between predicted pressure recovery and observed gradient differences was found (r = 0.90 and 0.85, respectively). Both the noncorrected and the corrected Doppler gradients correlated well with the catheter gradients (r = 0.93-0.97). However, noncorrected Doppler gradients significantly overestimated the catheter gradients (slopes, 1.36 and 1.25 for peak and mean gradients, respectively), while Doppler gradients corrected for pressure recovery showed good agreement with catheter gradients (slopes, 1.03 and 0.96; standard error of estimate [SEE] 8.1 and 6.9 mm Hg; mean difference +/- SD 0.4 +/- 8.0 mm Hg and 1.1 +/- 6.8 mm Hg for peak and mean gradients, respectively).nnnCONCLUSIONSnSignificant pressure recovery can occur in patients with aortic stenosis and can cause discrepancies between Doppler and catheter gradients. However, pressure recovery and the resulting differences between Doppler and catheter measurements may be predicted from Doppler velocity, aortic valve area and size of the ascending aorta.

Assessment of myocardial viability by dobutamine echocardiography, positron emission tomography and thallium-201 SPECT: Correlation with histopathology in explanted hearts

OBJECTIVESnWe examined the relationship among viability assessment by dobutamine echocardiography (DE), positron emission tomography (PET) and thallium-201 single-photon emission computed tomography (TI-SPECT) to the degree of fibrosis.nnnBACKGROUNDnDE, PET and TI-SPECT have been shown to be sensitive in identifying viability of asynergic myocardium. However, PET and TI-SPECT indicated viability in a significant percentage of segments without dobutamine response or functional improvement after revascularization.nnnMETHODSnTwelve patients with coronary artery disease and severely reduced left ventricular function (EF 14.5+/-5.2%) were studied with DE prior to cardiac transplantation: 5 had additional PET and 7 had TI-SPECT studies. Results of the three techniques were compared to histologic findings of the explanted hearts.nnnRESULTSnSegments with >75% viable myocytes by histology were determined to be viable in 78%, 89% and 87% by DE, PET and TI-SPECT; those with 50-75% viable myocytes in 71%, 50% and 87%, respectively. Segments with 25-50% viable myocytes showed response to dobutamine in only 15%, but were viable in 60% by PET and 82% by TI-SPECT. Segments with <25% viable myocytes responded to dobutamine in 19%; however, PET and TI-SPECT demonstrated viability in 33% and 38%, respectively. Discrepant segments without dobutamine response but viability by PET and SPECT had significantly more viable myocytes by pathology than did those classified in agreement to be nonviable but had significantly less viable myocytes than those classified in agreement to be viable (p < .001).nnnCONCLUSIONSnThese findings suggest that contractile reserve as evidenced by a positive dobutamine response requires at least 50% viable myocytes in a given segment whereas scintigraphic methods also identify segments with less viable myocytes. Thus, the methods may provide complementary information: Nuclear techniques appear to be highly sensitive for the detection of myocardial viability, and negative tests make it highly unlikely that a significant number of viable myocytes are present in a given segment. Conversely, dobutamine echo may be particularly useful for predicting recovery of systolic function after revascularization.

Importance of Pressure Recovery for the Assessment of Aortic Stenosis by Doppler Ultrasound Role of Aortic Size, Aortic Valve Area, and Direction of the Stenotic Jet In Vitro

BACKGROUNDnPressure recovery has been shown to occur distal to aortic stenoses in experimental and clinical studies. However, its clinical relevance in this setting has not yet been evaluated.nnnMETHODS AND RESULTSnTo address the hypothesis that pressure recovery can cause significant differences between Doppler and catheter gradients in aortic stenosis and to examine the effects of aortic size, aortic valve area, and direction of the stenotic jet on these differences, stenoses with valve areas from 0.5 to 1.25 cm2 and aortic diameters from 1.8 to 5.0 cm were studied in a pulsatile flow model. Jets entered the aorta centrally or eccentrically with angles of 15 degrees, 30 degrees, or 45 degrees. Overall, good correlation was found between Doppler and catheter gradients. However, when the various combinations of orifices and aortas were analyzed separately, slopes varied from 1.0 to 1.86, and the Doppler-catheter gradient differences ranged from -2 (small valve area with a large aorta) to 66 mm Hg (80% overestimation by Doppler echocardiography) when the stenosis was moderate and the aorta was small. Mild eccentricity of the jet did not significantly alter the results. However, overestimation by Doppler decreased with increasing jet eccentricity. Finally, differences between Doppler and catheter gradients could be predicted by estimating pressure recovery from Doppler measurements.nnnCONCLUSIONSnSignificant pressure recovery can occur in aortic stenosis and can cause differences between Doppler and catheter gradients. These differences may reach clinical relevance, particularly when the stenosis is moderate and the aorta is small and can be predicted from Doppler measurements.

Intraoperative Transesophageal Echocardiography in Valve Replacement Surgery

Transesophageal echocardiography (TEE) is applied widely during heart valve replacement surgery. Intraoperative TEE (IOTEE) is used to formulate the surgical plan, assess cardiac function, and evaluate surgical outcome. This review describes the methodology of IOTEE, focusing on its role in valve replacement surgery. Specific aspects, such as its role in surgical decision making, selection of the prosthetic model and size, detection and quantification of paravalvular leaks, outflow tract obstruction, and acute prosthetic valve obstruction, are discussed. Furthermore, a description of the value of IOTEE in newer procedures, such as port access surgery, is presented.

Asymptomatic Severe Aortic Stenosis in the Elderly

OBJECTIVESnThis study sought to assess the natural history and optimal timing of surgery in elderly patients with severe asymptomatic aortic stenosis (AS).nnnBACKGROUNDnAS is increasingly diagnosed in an aging population, and large numbers of elderly patients are undergoing aortic valve procedures. However, the average age of patients represented in most natural history studies on AS is between 60 and 70 years.nnnMETHODSnA total of 103 consecutive patients >70 years of age (51 female; mean age 77 ± 5 years) with asymptomatic severe AS (peak aortic jet velocity [AV-Vel] 4.7 ± 0.6 m/s) were prospectively followed.nnnRESULTSnDuring follow-up, 91 events occurred, including an indication for aortic valve replacement in 82 patients and cardiac deaths in 9, respectively. Event-free survival was 73%, 43%, 23%, and 16% at 1, 2, 3, and 4 years, respectively. Physical mobility was impaired in 29% of the patients, and symptom onset was severe (New York Heart Association functional classxa0≥III) in 43% of those who developed symptoms. Patients with AV-Velxa0≥5.0 m/s had event-free survival rates of 21% and 6% at 2 and 4 years, respectively, compared with 57% and 23% for patients with AV-Velxa0<5.0 m/s (pxa0<xa00.001). Seventy-one patients underwent aortic valve replacement, and post-operative survival was 89% and 77% after 1 and 3 years, respectively.nnnCONCLUSIONSnIn elderly patients with severe but asymptomatic AS, mild symptoms may be difficult to detect, particularly when mobility is impaired and severe symptom onset is common, warranting close clinical follow-up. Furthermore, a very high event rate can be expected, and cardiac deaths are not infrequent. Thus, elective aortic valve procedures may be considered in selected elderly patients at low procedural risk.

Relationship between dobutamine response of dyssynergic myocardium and angiographically documented blood supply

OBJECTIVEnBecause hibernation is considered a down-regulation of contractile function in response to reduced regional myocardial perfusion, hibernating myocardium is expected to be supplied by a critically stenosed or even occluded coronary artery. Thus, high-dose dobutamine has been postulated to cause ischemia and reworsening of myocardial function (biphasic response), whereas myocardium that demonstrates sustained improvement with high-dose dobutamine should not be supplied by a significantly stenosed vessel. This study evaluates the type of dobutamine response-biphasic versus sustained improvement-of dyssynergic myocardium in relation to its angiographically documented blood supply.nnnMETHODSnIn 38 patients (5 women; mean age 60 +/- 9 years) with chronic coronary artery disease and impaired left ventricular ejection fraction (</=35%), dobutamine echocardiography and quantitative coronary angiography were performed within 4 weeks. Wall-motion response of dyssynergic myocardium to dobutamine, classified as no improvement, biphasic response, or sustained improvement, was compared with the angiographically documented blood supply (presence of coronary stenosis in the corresponding artery, collaterals, and stenoses of the collateral supplying artery) in a segment-by-segment analysis.nnnRESULTSnOf the 465 segments with abnormal wall motion at rest, 201 (47%) showed improvement during dobutamine infusion at low dose. Of these, 145 (72%) were supplied by significantly stenosed epicardial vessels. Only 27 (19%) of these 145 segments showed a biphasic response whereas in the remaining 118 segments wall-motion improvement persisted during high-dose dobutamine infusion. Although mean stenosis severity in the supplying vessel was significantly greater for segments presenting with biphasic response as compared with sustained improvement (95 +/- 7% and 86 +/- 12% luminal diameter reduction, respectively; P <.0001), 69% of segments with sustained improvement were supplied by a critically stenosed artery. Only 7 of 27 segments with biphasic response and 22 of 118 segments with sustained improvement had visible collaterals supplied by a vessel without significant stenosis. The percentage of segments viable by thallium-single photon emission computed tomography imaging was similar for those with sustained and biphasic response (96% and 83%, respectively).nnnCONCLUSIONSnIn this group of patients with coronary artery disease and impaired left ventricular function, the great majority of dyssynergic segments that exhibited a sustained, rather than biphasic, dobutamine response were supplied by a critically stenosed artery. Furthermore, the percentage of segments viable by thallium-single photon emission computed tomography did not appear to be different for segments with sustained improvement and those with biphasic response. These findings challenge the hypothesis that biphasic response is the best criterion to identify viable myocardium.