Biomedical subjects

Mark D Handschumacher

Publications and source records attributed to Mark D Handschumacher.

10 recordsLinked to original sources

PubMed2006

Geometric determinants of functional tricuspid regurgitation: insights from 3-dimensional echocardiography.

BACKGROUND: Tricuspid regurgitation (TR) is an important predictor of morbidity and mortality in heart failure. We aimed to examine the 3D geometry of the tricuspid valve annulus (TVA) in patients with functional TR, comparing them with patients with normal tricuspid valve function and relating annular geometric changes to functional TR. METHODS AND RESULTS: TVA shape was examined by real-time 3D echocardiography in 75 patients: 35 with functional TR and 40 with normal tricuspid valve function (referent group). The 3D shape of the TVA was reconstructed from rotated 2D planes, and the annular plane was computed by least-squares fitting. Annular area and mediolateral, anteroposterior, and high (superior)-low (inferior) distances were calculated. TR was assessed by vena contracta width. The normal TVA has a bimodal pattern (high-low distance=7.23+/-1.05 mm). High points were located anteroposteriorly, and low points were located mediolaterally. With moderate or greater TR (vena contracta width 5.80+/-2.62 mm), the TVA became dilated (17.24+/-4.75 versus 9.83+/-2.18 cm2, P<0.0001, TR versus referent), more planar with decreased high-low distance (4.14+/-1.05 mm), and more circular with decreased ratio of mediolateral/anteroposterior (1.11+/-0.09 versus 1.32+/-0.09, P<0.0001, TR versus referent). CONCLUSIONS: The normal TVA has a bimodal shape with distinct high points located anteroposteriorly and low points located mediolaterally. With functional TR, the annulus becomes larger, more planar, and circular. These changes in annular shape with TR have potentially important mechanistic and therapeutic implications for tricuspid valve repair.

Arrhythmias, Cardiac↗

PubMed2005

The prognostic value of post-exercise blood pressure reduction in patients with hypertensive response during exercise stress test.

BACKGROUND: Hypertensive response at peak-exercise and during the recovery phase of exercise stress test (ET) is associated with poor cardiovascular prognosis. We investigated whether decrease in blood pressure (BP) from peak to post-exercise would identify a subgroup at higher cardiovascular risk. METHODS: Eighty-six non-hypertensive patients (0-4 cardiovascular risk factors) with hypertensive reaction at peak-ET (systolic>180 mm Hg and/or diastolic>100 mm Hg) were divided based on BP 5 min after exercise termination into two groups: Normal response (NrmR) (<160/90 mm Hg), Hypertensive response (HypR) (>/=160/90 mm Hg). Five years later the prevalence of cardiovascular risk factors and cardiovascular morbidity and mortality was assessed for each group. RESULTS: Both groups had similar pre- and peak-exercise BP. However the HypR group had higher post-exercise BP (systolic: 163+/-13 vs. 125+/-14 mm Hg, respectively, p<0.01, and diastolic: 74+/-6 vs. 75+/-4 mm Hg, respectively, p<0.01), smaller decrease in BP after exercise (Delta systolic: 46.9+/-3.1 vs. 73.9+/-3.6 mm Hg, respectively, p<0.01, Delta diastolic: 12.4+/-1.5 vs. 26.5+/-2.2 mm Hg, respectively, p<0.01), and higher post- than pre-exercise BP (Delta systolic: 24.5+/-3.5 vs. -6+/-4.1 mm Hg, respectively, p<0.01, A diastolic: 19+/-2.1 vs. -13+/-2.3 mm Hg, respectively, p<0.01). Five years later, HypR group had higher prevalence of abnormal cholesterol serum level (p<0.01), hypertension (p<0.01) and combined ischemic heart disease and cerebrovascular disease (RR 1.32, 95% CI=1.13-1.54, p<0.01). CONCLUSION: During ET evaluation, it is important to evaluate the BP at 5 min after exercise because reduced BP drop, at this routinely measured point, identifies a subgroup with higher cardiovascular risk.

Aged↗

PubMed2005

Usefulness of three-dimensionally guided assessment of mitral stenosis using matrix-array ultrasound.

Two-dimensional (2-D) planimetry is limited by the technical demands, time, and observer variability required to locate the minimal orifice area, limiting the confident clinical reporting of mitral valve area (MVA). In 27 consecutive patients, MVA was determined independently by 2 observers using the conventional 2-D method and a new 3-D-guided method. Using a matrix-array probe, the valve was visualized in a long-axis view and a cursor steered to intersect the leaflet tips and provide a perpendicular short-axis plane viewed side-by-side. Two-dimensional and 3-D-guided methods allowed planimetry in 24 patients. Consistent with better orifice localization, 3-D guidance eliminated the overestimation of internal orifice diameters in the planimetered short-axis view relative to the limiting diameter defined by the long-axis view (for 3-D guidance, 0.73 +/- 0.20 vs 0.73 +/- 0.21 cm, p = 0.98, vs 0.90 +/- 0.27 cm in the 2-D short-axis view, p <0.01). Accordingly, mean values for the smallest orifice area by 3-D guidance were less than by 2-D imaging (1.4 +/- 0.5 vs 1.5 +/- 0.5 cm(2), p <0.01), changing the clinical severity classification in 11 of 24 patients (46%). The 2-D method also overestimated MVA relative to 3-D guidance compared with Doppler pressure halftime and (n = 6) Gorlin areas. Phantom studies verified no differences in resolution for the 2 acquisition modes. Three-dimensional guidance reduced intraobserver variability from 9.8% to 3.8% (SEE 0.14 to 0.06 cm(2), p <0.01) and interobserver variability from 10.6% to 6.1% (SEE 0.15 to 0.09 cm(2), p <0.02). In conclusion, matrix-array technology provides a feasible and highly reproducible direct 3-D-guided method for measuring the limiting mitral orifice area.

Adult↗

PubMed2005

Quantitative assessment of regional myocardial function in mice by tissue Doppler imaging: comparison with hemodynamics and sonomicrometry.

BACKGROUND: Tissue Doppler imaging (TDI) is a novel echocardiographic method to quantify regional myocardial function. The objective of this study was to assess whether myocardial velocities and strain rate (SR) could be obtained by TDI in mice and whether these indices accurately quantified alterations in left ventricular (LV) systolic function. METHODS AND RESULTS: TDI was performed in 10 healthy mice to measure endocardial (v(endo)) and epicardial systolic velocities and SR. In further experiments, TDI indices were compared with dP/dt(max) and with sonomicrometer-derived regional velocities, at rest and after administration of dobutamine or esmolol. TDI indices were also studied serially in 8 mice before and 4 and 7 hours after endotoxin challenge. Myocardial velocities and SR were obtained in all mice with low measurement variability. TDI indices increased with administration of dobutamine (v(endo) from 2.2+/-0.3 to 3.8+/-0.2 cm/s [P<0.01]; SR from 12+/-2 to 20+/-2 s(-1) [P<0.05]) and decreased with administration of esmolol (v(endo) 1.4+/-0.2 cm/s [P<0.05]; SR 6+/-1 s(-1) [P<0.01]). Both indices correlated strongly with dP/dt(max) (r2=0.79 for SR and r2= 0.69 for v(endo); both P<0.0001). SR and shortening fraction were predictors of dP/dt(max) even after adjustment for the confounding effect of the other variables. V(endo) correlated closely with sonomicrometer-measured velocity (r2=0.71, P<0.0005). After endotoxin challenge, decreases in both v(endo) and SR were detected before decreases in shortening fraction became manifest. CONCLUSIONS: Myocardial velocities and SR can be measured noninvasively in mice with the use of TDI. Both indices are sensitive markers for quantifying LV global and regional function in mice.

Animals↗

PubMed2003

Leaflet concavity: a rapid visual clue to the presence and mechanism of functional mitral regurgitation.

Repairing mitral regurgitation (MR) requires an understanding of its mechanism. Evaluating restricted leaflet closure in functional MR is challenging. Tenting area between leaflets and annulus in long-axis (LAX) views correlates with MR, but is positive even in control subjects; in the 4-chamber view, the incomplete mitral leaflet closure (IMLC) tenting pattern may be subtle and variable. We tested the hypothesis that leaflet concavity toward the left atrium in the LAX view, a rapid visual clue indicating abnormal tethering predominantly by intermediate chords, is a strong indicator of functional MR. We reviewed 90 patients: 40 with inferior myocardial infarction and ejection fraction > or = 50%; 40 with global left ventricular dysfunction and ejection fraction < 50%; and 10 control subjects. We assessed leaflet shape (concave or convex toward the left atrium) and maximum systolic proximal MR jet width in the LAX views. To quantify shape, we measured the leaflet concavity area between the anterior leaflet and a line connecting its ends. Conventional IMLC area was also assessed. Patients with leaflet concavity had significantly greater MR than those without this finding (jet width of 4.6 +/- 0.7 vs 0.5 +/- 0.1 mm, P <.0001), indicating mild-moderate versus trace MR, with differences comparable in those with inferior myocardial infarction and left ventricular dysfunction. Leaflet concavity area most strongly predicted MR by multivariate regression (R(2) = 0.7). Conventional IMLC area did not uniquely distinguish patients with or without MR and correlated more weakly with MR (R(2) = 0.30 vs 0.73). Mitral leaflet concavity in the LAX view provides rapid and reliable recognition of functional MR, with greater reliability than IMLC area. This shape, consistent with tethering by intermediate chords, may have implications for potential intervention.

Aged↗

PubMed2003

Illusion of contraction from out-of-plane translation: can Doppler tissue velocities resolve it?

BACKGROUND: Assessment of wall motion is one of the most challenging aspects of echocardiography. Because of tapering cardiac shape, the impression of thickening can be produced by cardiac translation perpendicular to the image plane. Doppler tissue imaging (DTI) can potentially resolve this problem because in noncontracting myocardium, velocities (V) are uniform (V gradient [VG] = 0) and V measured by DTI should be unaffected by translation perpendicular to the imaging beam. METHODS: A left ventricle-shaped phantom and a string model were translated at known angles to the ultrasound beam. Two-dimensional gray-scale, DTI, and M-mode images were acquired and analyzed. RESULTS: During translation perpendicular to the image plane, 2-dimensional and M-mode images of the ventricular model showed apparent wall thickening, but analysis of the DTI images showed that V and VG across the walls were near 0 (V = 0.04 +/- 0.1 cm/s; VG = 0.02 +/- 0.02/s). Translation of both models at various angles relative to an M-mode beam also created the impression of wall thickening. However, DTI accurately measured the angle-corrected V component toward the transducer (r > 0.98, P <.0001), and VG corresponded to rigid body motion (0.003 +/- 0.02/s). CONCLUSIONS: M-mode and 2-dimensional echocardiography images are subject to the illusion of myocardial thickening resulting from out-of-plane translation. Analysis of tissue Doppler V avoids such error by accurately measuring V components and VG, and it has the potential to improve assessment of left ventricular function.

Artificial Intelligence↗

PubMed2002

Reverse ventricular remodeling reduces ischemic mitral regurgitation: echo-guided device application in the beating heart.

BACKGROUND: In ischemic mitral regurgitation (MR), mitral leaflet closure is restricted by ventricular remodeling with displacement of the papillary muscles (PMs). Therapy is uncertain because ring annuloplasty does not alleviate PM displacement. We tested the hypothesis that echo-guided PM repositioning using an external device can reduce MR without compromising left ventricular (LV) function. METHODS AND RESULTS: We studied 10 sheep with ischemic MR produced by circumflex ligation with inferior infarction, 6 acutely and 4 eight weeks after myocardial infarction (MI). A Dacron patch containing an inflatable balloon was placed over the PMs and adjusted under echo guidance to reverse LV remodeling and reposition the infarcted PM. 3D echo assessed mitral valve geometric changes. In 7 sheep, sonomicrometry and Millar catheters assessed changes in end-systolic and end-diastolic pressure-volume relationships, and microspheres were injected to assess coronary flow. Moderate MR after MI resolved with patch application alone (n=3) or echo-guided balloon inflation, which repositioned the infarcted PM, decreasing the PM tethering distance from 31.1+/-2.5 mm after MI to 26.8+/-1.8 with patch (P<0.01; baseline=25.5+/-1.5). LV contractility was unchanged (end-systolic slope=3.4+/-1.6 mm Hg/mL with patch versus 2.8+/-1.6 after MI). Although there was a nonsignificant trend for a mild increase in stiffness constant (0.07+/-0.05 mL(-1) versus 0.05+/-0.03 after MI, P=0.06), LV end-diastolic pressure was unchanged as MR resolved. Coronary flow to noninfarcted regions was not reduced. CONCLUSIONS: An external device that repositions the PMs can reduce ischemic MR without compromising LV function. This relatively simple technique can be applied under echo guidance in the beating heart.

Angioplasty, Balloon↗

PubMed2002

Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: three-dimensional echocardiographic stereolithography and patient studies.

OBJECTIVES: This study tested the hypothesis that the impact of a stenotic aortic valve depends not only on the cross-sectional area of its limiting orifice but also on three-dimensional (3D) valve geometry. BACKGROUND: Valve shape can potentially affect the hemodynamic impact of aortic stenosis by altering the ratio of effective to anatomic orifice area (the coefficient of orifice contraction [Cc]). For a given flow rate and anatomic area, a lower Cc increases velocity and pressure gradient. This effect has been recognized in mitral stenosis but assumed to be absent in aortic stenosis (constant Cc of 1 in the Gorlin equation). METHODS: In order to study this effect with actual valve shapes in patients, 3D echocardiography was used to reconstruct a typical spectrum of stenotic aortic valve geometrics from doming to flat. Three different shapes were reproduced as actual models by stereolithography (computerized laser polymerization) with orifice areas of 0.5, 0.75, and 1.0 cm(2) (total of nine valves) and studied with physiologic flows. To determine whether valve shape actually influences hemodynamics in the clinical setting, we also related Cc (= continuity/planimeter areas) to stenotic aortic valve shape in 35 patients with high-quality echocardiograms. RESULTS: In the patient-derived 3D models, Cc varied prominently with valve shape, and was largest for long, tapered domes that allow more gradual flow convergence compared with more steeply converging flat valves (0.85 to 0.90 vs. 0.71 to 0.76). These variations translated into differences of up to 40% in pressure drop for the same anatomic area and flow rate, with corresponding variations in Gorlin (effective) area relative to anatomic values. In patients, Cc was significantly lower for flat versus doming bicuspid valves (0.73 +/- 0.14 vs. 0.94 +/- 0.14, p < 0.0001) with 40 +/- 5% higher gradients (p < 0.0001). CONCLUSIONS: Three-dimensional valve shape is an important determinant of pressure loss in patients with aortic stenosis, with smaller effective areas and higher pressure gradients for flatter valves. This effect can translate into clinically important differences between planimeter and effective valve areas (continuity or Gorlin). Therefore, valve shape provides additional information beyond the planimeter orifice area in determining the impact of valvular aortic stenosis on patient hemodynamics.

Adult↗

PubMed2002

Mechanistic insights into functional mitral regurgitation.

Effective valve repair in patients with mitral regurgitation (MR) demands an understanding of its mechanism. In patients with ischemic heart disease and functional MR, which doubles late mortality, normal leaflets are apically displaced. This reflects an altered balance of forces acting on the leaflets: increased tethering forces restricting closure, resulting from an altered geometry of leaflet attachments, and decreased ventricular forces acting to close the leaflets. Extensive evidence confirms a central and predominant role of tethering as the final common pathway inducing functional MR; left ventricular (LV) pressure dynamically modulates the orifice area. Because ischemic MR is a disease of the entire mitral complex, including the remodeling LV, reducing annular size alone is often ineffective. Undersizing rings attempts to compensate for tethering; new and potentially more effective strategies directly address tethering by infarct plication, papillary muscle repositioning with a localized patch, or basal chordal cutting to increase coaptational surface area without prolapse. A comprehensive understanding of the valve in its ventricular context, therefore, provides new opportunities for successful valve repair in patients.

Humans↗

PubMed2002

Effect of destructive pulse duration on the detection of myocardial perfusion in myocardial contrast echocardiography: In vitro and in vivo observations.

UNLABELLED: Myocardial perfusion is detected with contrast echocardiography by comparing a contrast-enhanced image with a baseline obtained before contrast injection (true baseline) or after myocardial bubble destruction after a high-power destructive pulse (postdestructive pulse baseline). Although it is assumed that all bubbles are destroyed by a destructive pulse insuring optimal contrast detection, this assumption has not been tested. In 18 participants we compared the videointensity (VI) differences among the contrast-enhanced image, the postdestructive pulse baseline, and the true baseline using both triggered high-mechanical index imaging and real-time imaging. VI difference was significantly greater for the true baseline with both techniques at all ventricular levels. The benefit of using a true baseline was less when the duration of the destructive pulse was increased. Similarly, we quantified VI in a flow phantom using continuous Optison (commercially available perfluoropropane-filled albumin microbubbles) (Amersham, Princeton, NJ) infusion and variable durations of destructive pulses. VI decreased with the duration of the destructive pulse and reached a plateau after a duration of 8 to 15 frames. The plateau reached after a long destructive pulse was dependent on flow rate and concentration and never reached a true baseline, unless concentration (<100 microL/L) and flow rate (<0.5 cm/s) were very low. IN CONCLUSION: (1) in clinical studies, the difference in VI between contrast-enhanced and baseline images is greater when true baseline is used; (2) the longer the destructive pulse, the closer the postdestructive pulse baseline to true baseline; and (3) this effect exists in all regions of the left ventricle.

Adult↗