Donald A. Severyn

Cross-comparison of cardiac output trending accuracy of LiDCO, PiCCO, FloTrac and pulmonary artery catheters

IntroductionAlthough less invasive than pulmonary artery catheters (PACs), arterial pulse pressure analysis techniques for estimating cardiac output (CO) have not been simultaneously compared to PAC bolus thermodilution CO (COtd) or continuous CO (CCO) devices.MethodsWe compared the accuracy, bias and trending ability of LiDCO™, PiCCO™ and FloTrac™ with PACs (COtd, CCO) to simultaneously track CO in a prospective observational study in 17 postoperative cardiac surgery patients for the first 4 hours following intensive care unit admission. Fifty-five paired simultaneous quadruple CO measurements were made before and after therapeutic interventions (volume, vasopressor/dilator, and inotrope).ResultsMean CO values for PAC, LiDCO, PiCCO and FloTrac were similar (5.6 ± 1.5, 5.4 ± 1.6, 5.4 ± 1.5 and 6.1 ± 1.9 L/min, respectively). The mean CO bias by each paired method was -0.18 (PAC-LiDCO), 0.24 (PAC-PiCCO), -0.43 (PAC-FloTrac), 0.06 (LiDCO-PiCCO), -0.63 (LiDCO-FloTrac) and -0.67 L/min (PiCCO-FloTrac), with limits of agreement (1.96 standard deviation, 95% confidence interval) of ± 1.56, ± 2.22, ± 3.37, ± 2.03, ± 2.97 and ± 3.44 L/min, respectively. The instantaneous directional changes between any paired CO measurements displayed 74% (PAC-LiDCO), 72% (PAC-PiCCO), 59% (PAC-FloTrac), 70% (LiDCO-PiCCO), 71% (LiDCO-FloTrac) and 63% (PiCCO-FloTrac) concordance, but poor correlation (r2 = 0.36, 0.11, 0.08, 0.20, 0.23 and 0.11, respectively). For mean CO < 5 L/min measured by each paired devices, the bias decreased slightly.ConclusionsAlthough PAC (COTD/CCO), FloTrac, LiDCO and PiCCO display similar mean CO values, they often trend differently in response to therapy and show different interdevice agreement. In the clinically relevant low CO range (< 5 L/min), agreement improved slightly. Thus, utility and validation studies using only one CO device may potentially not be extrapolated to equivalency of using another similar device.

Non-invasive assessment of myocardial recovery on chronic left ventricular assist device: Results associated with successful device removal

BACKGROUND Myocardial recovery may occur in patients with heart failure who are receiving left ventricular assist-device support, but identification of candidates for device removal remains challenging. We hypothesized that on-line quantitative echocardiography during trials of decreased device support alone or in combination with exercise cardiopulmonary testing can assess cardiac recovery to predict successful device removal. METHODS We studied 18 patients with severe heart failure, aged 45 +/- 19 years, who received 234 +/- 169 days of assist-device support as a bridge to transplantation. We used echocardiographic automated border detection from mid-ventricular short-axis images and non-invasive arterial pressure to measure beat-to-beat responses in 2 to 5 minute trials of decreased device flow. We also assessed maximal oxygen consumption in 14 patients who could exercise. RESULTS Six patients experienced myocardial recovery and underwent successful device removal; 12 remained device dependent. With transient, low assist-device flow, patients with device removal had increased echocardiographic stroke area of 27% +/- 36% vs -24% +/- 12% (p < 0.05) and fractional area change of 51% +/- 13% vs 23% +/- 11% (p < 0.05) in the patients who were device dependent. Estimates of pre-load-adjusted maximal power, a relatively load-independent index, were 6.7 +/- 2.1 mW/cm(4) in patients with successful device removal vs 1.2 +/- 1.2 mW/cm(4) in patients who were device dependent (p < 0.005). Maximal oxygen consumption was 17.2 +/- 1.4 ml/kg/min in patients with myocardial recovery vs 13.1 +/- 1.9 ml/kg/min in patients who were device dependent (p < 0.005) and correlated with pre-load-adjusted maximal power (r = 0.89, p < 0.001). Maximal oxygen consumption >16 ml/kg/min, increased stroke area, >40% increase in fractional area change, or pre-load-adjusted maximal power >4.0 mW/cm(4) with low device flow were associated with successful device removal (p < 0.05). CONCLUSIONS On-line quantitative echocardiography alone or combined with exercise cardiopulmonary testing can assess myocardial recovery of patients receiving left ventricular assist-device support and has the potential to identify patients who are clinical candidates for device removal.

Ability of pulse power, esophageal Doppler, and arterial pulse pressure to estimate rapid changes in stroke volume in humans

Introduction:Measures of arterial pulse pressure variation and left ventricular stroke volume variation induced by positive-pressure breathing vary in proportion to preload responsiveness. However, the accuracy of commercially available devices to report dynamic left ventricular stroke volume variation has never been validated. Methods:We compared the accuracy of measured arterial pulse pressure and estimated left ventricular stroke volume reported from two Food and Drug Administration–approved aortic flow monitoring devices, one using arterial pulse power (LiDCOplus™) and the other esophageal Doppler monitor (HemoSonic™). We compared estimated left ventricular stroke volume and their changes during a venous occlusion and release maneuver to a calibrated aortic flow probe placed around the aortic root on a beat-to-beat basis in seven anesthetized open-chested cardiac surgery patients. Results:Dynamic changes in arterial pulse pressure closely tracked left ventricular stroke volume changes (mean r2 .96). Both devices showed good agreement with steady-state apneic left ventricular stroke volume values and moderate agreement with dynamic changes in left ventricular stroke volume (esophageal Doppler monitor −1 ± 22 mL, and pulse power −7 ± 12 mL, bias ± 2 sd). In general, the pulse power signals tended to underestimate left ventricular stroke volume at higher left ventricular stroke volume values. Conclusion:Arterial pulse pressure, as well as, left ventricular stroke volume estimated from esophageal Doppler monitor and pulse power reflects short-term steady-state left ventricular stroke volume values and tract dynamic changes in left ventricular stroke volume moderately well in humans.

Enhancement of tissue factor expression by vein segments exposed to coronary arterial hemodynamics

PURPOSE Although saphenous vein is the most reliable conduit for arterial interposition procedures in the coronary circulation, graft thrombosis remains a clinical problem. We hypothesized that an important factor in early graft thrombosis is sudden change in the hemodynamic environment of the vein as it is placed in the coronary circulation. METHODS We used an ex vivo perfusion system to study freshly excised segments of human saphenous vein (HSV) and pig internal jugular vein. For coronary graft (CAVG) simulation, sections of HSV were subjected to arterial pulsatile pressure and flow and twisting and stretching to mimic deformations caused by the beating heart. Using functional and immunohistochemical assays, we investigated the effect of these conditions on expression of tissue factor (TF), an important prothrombotic surface molecule. RESULTS In each of 11 experiments (6 human, 5 porcine), vein segments from a single donor were subjected to venous conditions (VEN), CAVG perfusion, or no perfusion. Expression of TF was measured as the amount of factor Xa generated per unit area of luminal vein surface. VEN perfusion did not cause a significant change in mean TF expression over nonperfused control values (human: 14.3 +/- 1.5 versus 11.4 +/- 2.3 U/cm2, p = 0.31; pig: 11.6 +/- 1.5 versus 12.5 +/- 1.4 U/cm2, p = 0.70). CAVG perfusion led to significant enhancement of TF expression over VEN perfusion (human: 36.8 +/- 6.2 versus 14.3 +/- 1.5 U/cm2, p < 0.05; pig: 40.0 +/- 9.9 versus 11.6 +/- 1.5 U/cm2, p < 0.05). Immunohistochemical analysis showed positive TF staining on the luminal side of a CAVG-stimulated HSV segment, but not on a VEN-stimulated segment. In four additional studies, HSV segments were subjected to arterial perfusion without twist and stretch to mimic lower extremity arterial interposition grafts. TF expression for lower extremity venous graft perfusion was significantly higher than for VEN perfusion (25.3 +/- 2.5 versus 14.3 +/- 1.5, p < 0.01) but not significantly different from CAVG perfusion. CONCLUSIONS Our studies in a unique perfusion system suggest that exposure of vein to coronary arterial hemodynamic conditions results in elevated expression of the important prothrombotic molecule TF. This phenomenon may contribute to early graft thrombosis.

Regional correlation by color-coded tissue Doppler to quantify improvements in mechanical left ventricular synchrony after biventricular pacing therapy

Cardiac resynchronization therapy (CRT) can improve cardiac function in patients with heart failure and left bundle branch block. To test a new synchrony index derived from mitral annular velocity by color tissue Doppler, 19 subjects were studied: 9 patients with heart failure and left bundle branch block at baseline and at 1, 3 and 6 months after CRT and 10 normal controls. The synchrony index in patients with heart failure was less than that in controls at baseline (r = 0.60 +/- 0.13 vs 0.94 +/- 0.02; p <0.01), but improved at 6 months after CRT (r = 0.77 +/- 0.09; p <0.05 vs baseline).

Second-generation tissue Doppler with angle-corrected color-coded wall displacement for quantitative assessment of regional left ventricular function

To test the hypothesis that a new tissue Doppler (TD) approach using angle-correction and transformation of velocity data to color-coded displacement data may objectively quantify regional left ventricular function, in vitro experiments were first performed with an oscillating echo target precisely controlled by a microstepping motor. Displacement varied from 1 to 15 mm (60 to 130 cycles/min) at angles of 0 degrees and 45 degrees to the echo transducer. Custom software transformed TD data to displacement data. Sixty-five subjects were then studied: 35 with wall motion abnormalities and 30 normal controls. Results were compared with independent visual assessment and caliper measurements of endocardial excursion from gray-scale images. In vitro displacement imaging strongly correlated with true displacement (r = 0.99, p <0.0001). In humans, peak transmural displacement discriminated normal results (6.3 +/- 3.2 mm) from hypokinesia (2.7 +/- 1.8 mm, p <0.05), akinesia (0.4 +/- 1.2 mm, p <0.05) from hypokinesia, and dyskinesia (-1.9 +/- 1.2 mm, p <0.05) from akinesia. Normal subendocardial displacement was 5.9 +/- 2.9 versus 4.0 +/- 3.9 mm in the epicardial layer (p <0.01). This displacement gradient was absent in abnormal segments. Displacement data correlated with endocardial excursion by calipers (parasternal views: r = 0.86, all views: r = 0.79, both p <0.0001). Overall accuracy of displacement imaging was 82% (kappa = 0.71) versus 66% (kappa = 0.43) for visual assessment with caliper data as the standard of reference. Angle-corrected displacement imaging was superior to routine visual assessment and is a promising new method to quantify regional left ventricular function.

Effect of retroviral transduction on human endothelial cell phenotype and adhesion to Dacron vascular grafts

PURPOSE Retroviral transduction for genetic enhancement of endothelial cell (EC) anti-thrombotic phenotype offers potential for improving the clinical success of vascular graft seeding; however, application of this technique may bring concomitant alteration in cell functionality. METHODS Human microvascular ECs were transduced with a retroviral vector encoding for the marker gene beta-galactosidase. Transduced endothelial cells (rtECs) and nontransduced endothelial cells (ntECs) were evaluated by flow cytometry for expression of intercellular adhesion molecule (ICAM)-1 and tissue factor (TF) on both smooth (coverslips) and graft (Dacron, 6 mm inside diameter) surfaces under static and shear exposed conditions. Graft EC retention was measured after 6-hour pulsatile perfusions. Platelet and neutrophil adherence was measured on perfused coverslips. RESULTS Lower levels of ICAM-1 were expressed by rtECs on coverslips under both static (p < 0.01 vs static ntECs) and shear exposed conditions (p < 0.01 vs static and shear ntECs). Accordingly, fewer polymorphonuclear leukocytes adhered to rtEC monolayers (p < 0.01 vs ntECs). No difference in ICAM-1 and TF expression by static graft seeded rtECs and ntECs was observed. However, graft-seeded rtECs that were exposed to wall shear stress displayed less TF than sheared ntECs (p < 0.05). Transduction did not affect EC retention to the sheared graft surface. CONCLUSIONS These data suggest that retroviral transduction does not elicit a prothrombotic/proinflammatory phenotype, rather indices of these states appear in some conditions to be reduced. Further, transduction does not adversely affect EC adherence to Dacron graft surfaces under arterial hemodynamics.

Monitoring patients with continuous-flow ventricular assist devices outside of the intensive care unit: novel challenges to bedside nursing

Ventricular assist devices provide therapeutic options for patients with severe heart failure who have exhausted available medical therapies. With restoration of organ perfusion with ventricular assist devices, the heart failure resolves and quality of life and functional status improve. The current generation of continuous-flow devices present novel challenges to the clinical assessment of patients by substantially reducing or nearly eliminating any palpable pulse. Patients therefore generally have inadequate arterial pulsatility for most noninvasive monitoring devices such as pulse oximeters or automated blood pressure cuffs to work accurately. This article describes the function of continuous-flow devices and how this function affects common monitoring options, as well as how to clinically assess recipients of continuous-flow devices to promptly identify those whose condition may be deteriorating or who may be receiving inadequate perfusion.

Bariatric surgery for a patient with a HeartMate II ventricular assist device for destination therapy

A patient with a HeartMate II left ventricular assist device who had a body mass index of 52 needed gastric bypass surgery in order to qualify for a heart transplant. Unlike previous experience in which the surgery was performed at the implant hospital, the gastric bypass surgery in this case was performed at a bariatric center of excellence that was a separate facility from the implant hospital. The artificial heart program of the University of Pittsburgh Medical Center worked with the bariatric center of excellence in scheduling the gastric bypass surgery using a multidisciplinary team approach at 2 hospitals to coordinate safe, high-quality patient care in a unique situation.

Quantification of acute reduction in mitral regurgitation following cardiac resynchronization therapy

Background: Cardiac resynchronization therapy (CRT) is associated with delayed improvements in cardiac function in heart failure patients with left bundle branch block (LBBB) secondary to reverse remodeling. However, the mechanisms of immediate benefits from CRT pacing are not well understood. Our objective was to assess the acute effects of CRT pacing on mitral regurgitation (MR) using quantitative volumetric Doppler echocardiography. Methods: Twenty-four HF patients with LBBB, aged 66 10 yrs, with ejection fraction of 25 7% and QRS duration of 168 35 ms were studied by quantitative 2-D and Doppler echocardiography at baseline and the day after CRT biventricular pacing therapy. MR was quantified with the volumetric method and expressed as regurgitant volume and regurgitant fraction, in addition to and digital color regurgitation jet area. MR regurgitant volume was obtained by subtracting left ventricular outflow tract stroke volume from mitral inflow stroke volume, determined by their respective time velocity integrals multiplied by cross-sectional area. MR regurgitant fraction was obtained by dividing regurgitant volume by mitral inflow stroke volume. Results: Baseline group mean MR regurgitant volume was 35 24 ml, MR regurgitant fraction was 35 17% and MR jet area was 6.9 4.9 cm. After only 23 10 hours of CRT, significant improvements in MR occurred with regurgitant volume decreasing to 20 19 ml* and MR regurgitant fraction decreasing to 21 16%*, (*p 0.01 vs. baseline) (figure). MR jet area also decreased to 5.0 5.1 cm (p 0.05 vs. baseline). Acute reductions in MR were accompanied by a significant improvement in cardiac index from 2.1 0.5 to 2.4 0.6* L/min/m (*p 0.05 vs. baseline). Conclusion: CRT resulted in acute significant reductions in MR and increases in cardiac index. These data support MR reduction as an important acute beneficial effect of CRT in HF patients with LBBB.