Three-dimensional versus two-dimensional echocardiographic assessment of functional mitral regurgitation proximal isovelocity surface area.

BACKGROUND: The geometric shape of the mitral regurgitation (MR) proximal isovelocity surface area (PISA) is conventionally assumed to be a hemisphere (HS). However, in functional MR, PISA is frequently neither an HS nor a hemiellipse (HE) but is often asymmetric and crescent shaped. We used 3-dimensional transesophageal echocardiographic (3D TEE), full-volume data sets to directly measure the PISA and subsequently compared calculated values of effective regurgitant orifice area (EROA) with conventional 2D TEE techniques. EROA calculations from all PISA measurements were finally compared with the cross-sectional area at the vena contracta, a well-validated reference measure of the functional MR orifice area. METHODS: Twenty-four cardiac surgical patients with functional MR, who underwent routine intraoperative TEE examinations with a 3D matrix array probe (X7-2t; IE33; Philips Healthcare, Inc., Andover, MA) were retrospectively evaluated for MR severity using quantitative 2D and 3D TEE-derived techniques. Conventional 2D TEE methods were used to estimate PISA assuming an HS shape and an HE shape. In addition, direct measurement of the 3D PISA was obtained (QLab, Philips Healthcare, Inc.) from corresponding full-volume, color-flow Doppler data sets. EROAs calculated from HS- and HE-PISA techniques were compared with the same values obtained from 3D TEE PISAs. EROAs obtained from all 3 PISA techniques were subsequently compared with vena contracta area. RESULTS: Three-dimensional PISA was significantly larger than both HS-PISA and HE-PISA (mean ± SD: 4.65 ± 2.03 cm² vs 2.10 ± 1.58 cm² and 2.75 ± 1.42 cm²; both P < 0.0001), respectively. HE-PISA was also larger than HS-PISA (P = 0.042). In addition, 3D EROA was larger than both HS- and HE-acquired EROAs (mean ± SD: 0.44 ± 0.21 vs 0.19 ± 0.12 cm² and 0.26 ± 0.14; both P < 0.0001), respectively, while HE-EROA was larger than HS-EROA (P = 0.024). Vena contracta area correlated well with 3D EROA (Spearman r = 0.865), HS-EROA (Spearman r = 0.820; P < 0.001) and HE-EROA (Spearman r = 0.819). However, the difference between vena contracta area and 3D EROA was significantly less than the differences between vena contracta area and either 2D HS- or 2D HE-EROA (P < 0.0001). CONCLUSIONS: Quantitative assessment of functional MR severity by 3D TEE may be superior to 2D methods by permitting more direct measures of PISA. Two-dimensional TEE techniques for assessing functional MR severity that rely on an HS- or HE-PISA shape may underestimate the EROA due to geometric assumptions that do not account for asymmetry.

Sex differences in the prevalence of diastolic dysfunction in cardiac surgical patients.

OBJECTIVES: The mortality from diastolic dysfunction is approximately 9% to 28%. In patients with ischemic heart disease, female sex and advanced age are associated with increases in ventricular diastolic stiffness. Clinical studies have found higher rates of diastolic dysfunction in women, despite higher ejection fractions, than in men post-myocardial infarction. Therefore, we hypothesized that female patients undergoing cardiac surgery have higher degrees of diastolic dysfunction and experience more adverse outcomes, such as prolonged hospitalization. METHODS: We prospectively enrolled 153 patients undergoing cardiac surgery. Diastolic function was assessed using early transmitral velocity (E) and early diastolic lateral mitral annular tissue velocity (e'). Left ventricular diastolic dysfunction was defined as binary and a continuous outcome (E/e'). RESULTS: Females were more likely than males to present with higher E/e' (11.5 vs. 7.9, p = 0.001) and higher left ventricular diastolic dysfunction (71% vs. 36%, p < 0.001). The addition of sex to the model for left ventricular diastolic dysfunction was significant. The relationship between sex and E/e' ratio showed the biggest difference between males and females in the 56-72-year-old age brackets, where women were much more likely to have a higher E/e' than males. CONCLUSIONS: We identified a significantly higher prevalence of diastolic dysfunction among females presenting for elective cardiac surgery compared to males. This finding is more pronounced with age. Additionally, we found that female sex is at higher risk of prolonged ICU and hospital length of stay.

Echocardiographic evaluation of mitral inflow hemodynamics after asymmetric double-orifice repair.

BACKGROUND: A comprehensive transesophageal echocardiographic (TEE) examination is essential for the evaluation of a mitral valve (MV) repair. The edge-to-edge MV repair (i.e., Alfieri stitch) can pose a unique challenge in assessing iatrogenic mitral stenosis, especially when an asymmetric double-orifice is created. The reliability of the simplified Bernoulli equation for evaluating transvalvular pressure gradients across an asymmetric Alfieri MV repair remains controversial. We sought to evaluate the reliability of this principle further by comparing TEE-acquired pressure gradients across each orifice in patients undergoing asymmetric, double-orifice repair. METHODS: Routinely collected intraoperative, 2-dimensional and 3-dimensional TEE datasets acquired from 15 patients undergoing double-orifice MV repair were retrospectively reviewed and analyzed. Planimetered anterior lateral (AL) and posterior medial (PM) orifice areas were acquired from 3-dimensional TEE full volume datasets, by cropping the image to develop a short-axis view at the narrowest diastolic orifice cross-sectional area at the MV leaflet tips. Transmitral Doppler flow velocity values were measured through the AL and PM orifices. Peak and mean pressure gradients were calculated from the simplified Bernoulli equation at both orifices and were compared to each respective orifice for each patient. RESULTS: The mean difference between the AL and PM orifice areas for each patient was statistically significant (0.72 ± 0.40 cm(2), P < 0.0001). The mean differences between the AL and PM parameters were also significant for peak velocity: 0.15 m/s, SD: 0.08, P < 0.0001; peak pressure gradients: 1.76 mm Hg, SD: 1.42, P < 0.0001; and mean pressure gradient: 1.04 mm Hg, SD: 0.93, P < 0.0001. CONCLUSIONS: The echocardiographic assessment of MV dysfunction after an Alfieri repair is important. Although the differences that we demonstrated between orifice areas and maximum velocities across the asymmetric orifices after a double-orifice MV repair are statistically significant, the corresponding difference in mean transorifice pressure gradient is not clinically relevant. Thus, either orifice can be interrogated with Doppler echocardiography for the determination of pressure gradients after double-orifice MV repair.

Adaptations for avian frugivory: assimilation efficiency and gut transit time of Manacus vitellinus and Pipra mentalis.

I examined the digestive physiology of two avian frugivores, the golden-collared manakin, Manacus vitellinus, and the red-capped manakin, Pipra mentalis, to discover how these birds extract energy from fruit. Using 14 species of fruit in the natural diet of manakins, I examined the assimilation of nutrients from fruit pulp, fruit passage rates, seed passage rates, and gut morphology. Fruits in the manakins' diets had high water content (average, 84%) and low nutrient concentrations (3 kJ/g wet pulp; 17 kJ/g dry pulp; 1% nitrogen/g dry pulp). Manacus and Pipra did not differ in the average assimilation of energy in fruit pulp (63%), although it varied from 37 to 84% depending on fruit species. Assimilation of total nonstructural carbohydrates in the fruit pulp was very high (86-98%) in both species. Gut evacuation was rapid; maximum transit time of a labeled fruit was 30 min. Seeds passed through the gut faster (Manacus: 15 min; Pipra: 12 min) than the accompanying fruit epidermis (both spp: 22 min). Manakins regurgitated large seeds (>5 mm diameter) in 7 to 9 min. Rapid gut passage time, high assimilation of nonstructural carbohydrates, and the selective regurgitation and rapid elimination of bulky seeds enable manakins to process a large volume of food per day. By increasing rates of fruit intake and gut passage, manakins can effectively increase total nutrient uptake. These adaptations of manakins are requisite for harvesting sufficient nutrients from fruit, due to its low nutrient density, high water content, and bulky seeds.

Right heart failure: an ischemic model and restraint therapy for treatment.

BACKGROUND: Right heart failure is poorly understood and treated. In left heart failure, ventricular restraint can reverse pathologic left ventricular remodeling. The effect of restraint in right heart failure, however, is not known. We hypothesize that ventricular restraint can be applied selectively to the right ventricle (RV) to promote RV reverse remodeling. METHODS: Right heart failure was induced by right coronary artery ligation in a sheep model. Eight weeks later, a saline-filled epicardial balloon was placed around the RV surface for restraint. Restraint level was defined by measuring balloon luminal pressure at end-diastole. Maximum balloon pressure was determined by the amount of balloon pressure required to decrease systemic mean arterial pressure by 10 mm Hg. We determined end-diastolic transmural myocardial pressure, indices of myocardial oxygen consumption, and RV diastolic compliance at 4 different restraint levels. RESULTS: After coronary ligation, RV ejection fraction (EF) decreased from 0.574±0.04 to 0.362±0.03 (p<0.05). End-diastolic RV volume increased from 70.8 mL/m2±9 to 82.2 mL/m2±7 (p<0.05) by magnetic resonance imaging. After application of restraint to the RV only, RV transmural pressure decreased significantly by 27%. Greater levels of restraint also improved RV EF (0.347±0.06 to 0.473±0.05) but did not change RV end-diastolic volume. CONCLUSIONS: A model of ischemic right heart failure was successfully created. Selective RV restraint results in improved mechanical efficiency, decreased wall stress, and improved EF. The benefits of restraint in right heart failure warrant further investigation.

Ischemic mitral regurgitation: mechanisms, intraoperative echocardiographic evaluation, and surgical considerations.

Ischemic mitral regurgitation (IMR) is a subcategory of functional rather than organic, mitral valve (MV) disease. Whether reversible or permanent, left ventricular remodeling creates IMR that is complex and multifactorial. A comprehensive TEE examination in patients with IMR may have important implications for perioperative clinical decision making. Several TEE measures predictive of MV repair failure have been identified. Current practice among most surgeons is to typically repair the MV in patients with IMR. MV replacement is usually reserved for situations in which the valve cannot be reasonably repaired, or repair is unlikely to be tolerated clinically.

Intraoperative evaluation of transmitral pressure gradients after edge-to-edge mitral valve repair.

OBJECTIVE: Edge-to-edge repair of the mitral valve (MV) has been described as a viable option used for the surgical management of mitral regurgitation (MR). Based on the significant changes in MV geometry associated with this technique, we hypothesized that edge-to-edge MV repairs are associated with higher intraoperative transmitral pressure gradients (TMPG) compared to conventional methods. METHODS: Patient records and intraoperative transesophageal echocardiography (TEE) examinations of 552 consecutive patients undergoing MV repair at a single institution over a three year period were assessed. After separation from cardiopulmonary bypass (CPB), peak and mean TMPG were recorded for each patient and subsequently analyzed. RESULTS: 84 patients (15%) underwent edge-to-edge MV repair. Peak and mean TMPG were significantly higher compared to gradients in patients undergoing conventional repairs: 10.7 ± 0.5 mmHg vs 7.1 ± 0.2 mmHg; P<0.0001 and 4.3 ± 0.2 mmHg vs 2.8 ± 0.1 mmHg; P<0.0001. Only patients with mean TMPG ≥ 7 mmHg (n = 9) required prompt reoperation for iatrogenic mitral stenosis (MS). No differences in peak and mean TMPG were observed among edge-to-edge repairs performed in isolation, compared to those performed in combination with annuloplasty: 11.0 ± 0.7 mmHg vs 10.3 ± 0.6 mmHg and 4.4 ± 0.3 mmHg vs 4.3 ± 0.3 mmHg. There were no differences in TMPG between various types of annuloplasty techniques used in combination with the edge-to-edge repairs. CONCLUSIONS: Edge-to-edge MV repairs are associated with higher intraoperative peak and mean TMPG after separation from CPB compared to conventional repair techniques. Unless gradients are severely elevated, these findings are not necessarily suggestive of iatrogenic MS. Thus, in the immediate postoperative period mildly elevated TMPG can be expected and tolerated after edge-to-edge mitral repairs.