Jan J. Schreuder

The double-orifice technique as a standardized approach to treat mitral regurgitation due to severe myxomatous disease: surgical technique

OBJECTIVES Mitral-valve repair in Barlows disease is challenging; conventional techniques are difficult to perform, and there is a high risk of a postoperative suboptimal result. Double-orifice repair has been applied in a standardized approach to treat patients with severe mitral regurgitation and bileaflet prolapse due to Barlows disease. METHODS Since 1993, 82 patients with severe mitral regurgitation due to Barlows disease underwent correction applying the edge-to-edge concept. They were submitted to double-orifice repair in a standardized fashion, suturing the middle portions of both leaflets. RESULTS There were no hospital deaths. The repair was unsatisfactory in one patient who underwent valve replacement soon after the repair. The mean postoperative valve area was 3.7+/-0.79 cm(2) against a mean preoperative value of 9.2+/-2.1 cm(2). No or mild regurgitation was found in all but three patients who showed moderate residual regurgitation. There were no late deaths. Freedom from reoperation was 86+/-14% at 5 years. At the latest follow-up, all patient but one were New York Heart Association (NYHA) functional class I, and echo-Doppler assessment of valve reconstruction showed stable valve function in all patients. CONCLUSIONS The double-orifice repair can be used as a standardized approach to treat valve regurgitation due to Barlow disease with low risk and good early and mid-term results.

An evaluation of cardiac output by five arterial pulse contour techniques during cardiac surgery.

The bias, precision and tracking ability of five different pulse contour methods were evaluated by simultaneous comparison of cardiac output values from the conventional thermodilution technique (COtd). The five different pulse contour methods included in this study were: Wesselings method (cZ); the Modelflow method; the LiDCO system; the PiCCO system and a recently developed Hemac method. We studied 24 cardiac surgery patients undergoing uncomplicated coronary artery bypass grafting. In each patient, the first series of COtd was used to calibrate the five pulse contour methods. In all, 199 series of measurements were accepted by all methods and included in the study. COtd ranged from 2.14 to 7.55 l.min−1, with a mean of 4.81 l.min−1. Bland‐Altman analysis showed the following bias and limits of agreement: cZ, 0.23 and − 0.80 to 1.26 l.min−1; Modelflow, 0.00 and − 0.74 to 0.74 l.min−1; LiDCO, – 0.17 and − 1.55 to 1.20 l.min−1; PiCCO, 0.14 and − 1.60 to 1.89 l.min−1; and Hemac, 0.06 and − 0.81 to 0.93 l.min−1. Changes in cardiac output larger than 0.5 l.min−1 (10%) were correctly followed by the Modelflow and the Hemac method in 96% of cases. In this group of subjects, without congestive heart failure, with normal heart rhythm and reasonable peripheral circulation, the best results in absolute values as well as in tracking changes in cardiac output were measured using the Modelflow and Hemac pulse contour methods, based on non‐linear three‐element Windkessel models.

Acute and short-term effects of partial left ventriculectomy in dilated cardiomyopathy: assessment by pressure-volume loops.

OBJECTIVES The aim of this study was to evaluate the short-term effects of partial left ventriculectomy (PLV) on left ventricular (LV) pressure-volume (P-V) loops, wall stress, and the synchrony of LV segmental volume motions in patients with dilated cardiomyopathy. BACKGROUND Surgical LV volume reduction is under investigation as an alternative for, or bridge to, heart transplantation for patients with end-stage dilated cardiomyopathy. METHODS We measured P-V loops in eight patients with dilated cardiomyopathy before, during and two to five days after PLV. The conductance catheter technique was used to measure LV volume instantaneously. RESULTS The PLV reduced end-diastolic volume (EDV) acutely from 141+/-27 to 68+/-16 ml/m2 (p < 0.001) and to 65+/-6 ml/m2 (p < 0.001) at two to five days postoperation (post-op). Cardiac index (CI) increased from 1.5+/-0.5 to 2.6+/-0.6 l/min/m2 (p < 0.002) and was 1.8+/-0.3 l/min/m2 (NS) at two to five days post-op. The LV ejection fraction (EF) increased from 15+/-8% to 35+/-6% (p < 0.001) and to 26+/-3% (p < 0.003) at two to five days post-op. Tau decreased from 54+/-8 to 38+/-6 ms (p < 0.05) and was 38+/-5 ms (NS) at two to five days post-op. Peak wall stress decreased from 254+/-85 to 157+/-49 mm Hg (p < 0.001) and to 184+/-40 mm Hg (p < 0.003) two to five days post-op. The synchrony of LV segmental volume changes increased from 68+/-6% before PLV to 80+/-7% after surgery (p < 0.01) and was 73+/-4% (NS) at two to five days post-op. The LV synchrony index and CI showed a significant (p < 0.0001) correlation. CONCLUSIONS The acute decrease in LV volume in heart-failure patients following PLV resulted at short-term in unchanged SV, increases in LVEF, and decreases in peak wall stress. The increase in LV synchrony with PLV suggests that the transition to a more uniform LV contraction and relaxation pattern might be a rationale of the working mechanism of PLV.

Single injection thermodilution : A flow-corrected method

Background Application of the Stewart-Hamilton equation in the thermodilution technique requires flow to be constant. In patients in whom ventilation of the lungs is controlled, flow modulations may occur leading to large errors in the estimation of mean cardiac output. Methods To eliminate these errors, a modified equation was developed. The resulting flow-corrected equation needs an additional measure of the relative changes of blood flow during the period of the dilution curve. Relative flow was computed from the pulmonary artery pressure with use of the pulse contour method. Measurements were obtained in 16 patients undergoing elective coronary artery bypass surgery. In 11 patients (group A), pulmonary artery pressure was measured with a catheter tip transducer, in a partially overlapping group of 11 patients (group B), it was measured with a fluid-filled system. For reference cardiac output we used the proven method of four uncorrected thermodilution estimates equally spread over the ventilatory cycle. Results A total of 208 cardiac output estimates was obtained in group A, and 228 in group B. In group B, 48 estimates could not be corrected because of insufficient pulmonary artery pressure waveform quality from the fluid-filled system. Individual uncorrected Stewart-Hamilton estimates showed a large variability with respect to their mean. In group A, mean cardiac output was 5.01 l/min with a standard deviation of 0.53 l/min, or 10.6%. After flow correction, this scatter decreased to 5.0% (P < 0.0001). With no bias, the corresponding limits of agreement decreased from plus/minus 1.06 to plus/minus 0.5 l/min after flow correction. In group B, the scatter decreased similarly and the limits of agreement also became plus/minus 0.5 l/min after flow correction. Conclusion It was concluded that a single thermodilution cardiac output estimate using the flow-corrected equation is clinically feasible. This is obtained at the cost of a more complex computation and an extra pressure measurement, which often is already available. With this technique it is possible to reduce the fluid load to the patient considerably.

Automated infusion of vasoactive and inotropic drugs to control arterial and pulmonary pressures during cardiac surgery

OBJECTIVE To evaluate the feasibility of a closed-loop system for simultaneous control of systemic arterial and pulmonary artery blood pressures during cardiac surgery. DESIGN Feasibility study. SETTING The cardiac surgery operating room. PATIENTS The performance of the multiple-drug closed-loop system was evaluated during cardiac surgery in 30 patients who required treatment with more than one vasoactive or inotropic drug. INTERVENTIONS A multiple-drug closed-loop system integrated five single-drug blood pressure controllers. Arterial hypertension was controlled using sodium nitroprusside or nitroglycerin, arterial hypotension was controlled using noradrenaline or dobutamine, and pulmonary hypertension was controlled using nitroglycerin. The anesthesiologist selected target pressures and single-drug blood pressure controllers. The multiple-drug closed-loop system had a set of priority rules that automatically activated from the selected single-drug controllers the optimum single-drug controller for each hemodynamic state. Drug infusion rates of the nonactive controllers were kept constant. The initial knowledge that was used to construct the priority rules was obtained from standard anesthetic protocols on perioperative management of cardiac surgical patients. A supervisory computer program defined the actions to be taken in cases of infusion pump problems, invalid pressure measurements, and during unexpected increases and decreases in systemic arterial pressure. MEASUREMENTS AND MAIN RESULTS The activation of single-drug controllers by the priority rules was accurate and fast. On average, a different single-drug controller was activated once every 7.2 mins. As a measure of variability, the average deviation of mean arterial pressure and mean pulmonary artery pressure from their target values was evaluated and was 8.6+/-4.0 and 4.4+/-4.0 mm Hg, respectively, before cardiopulmonary bypass and 8.0+/-3.6 and 2.4+/-0.9 mm Hg, respectively, after cardiopulmonary bypass. None of the single-drug controllers showed any signs of unstable response. CONCLUSION Closed-loop control of both arterial and pulmonary pressures using multiple drugs is feasible during cardiac surgery.

Mean cardiac output by thermodilution with a single controlled injection.

ObjectiveA new method to estimate mean cardiac output by thermodilution with a single duration-controlled injection was evaluated in patients. DesignProspective criterion standard study. SettingUniversity hospital cardiac surgical intensive care unit and cardiac operation room. PatientsOf 33 patients, 24 underwent coronary bypass graft surgery, four had a valve replacement, and five were treated in the intensive care unit. InterventionsInterventions consisted of thermodilution cardiac output measurements. One single duration-controlled injection of cold fluid was used to calculate cardiac output. This controlled injection was performed with a duration equal to one whole ventilation cycle of the ventilator. An algorithm adapted to this duration-controlled injection calculated cardiac output. Moreover, this algorithm has properties to reduce errors caused by artificial ventilation and thermal noise. Measurements and Main Results In 33 patients, the averaged values of four measurements equally spread over the ventilatory cycle (phase-controlled) were compared with the values of two single duration-controlled measurements. The measurements were performed during periods of stable respiration and circulation. No significant difference was observed between the mean of four phase-controlled measurements and the mean of the two duration-controlled measurements. The cardiac output values in the intensive care patients were significantly higher compared with the two other patient groups (p < .05). The difference between the two methods could not be subdivided for the three patient groups (p > .05). The coefficient of variation of the single duration-controlled thermodilution measurements was significantly lower than the single phase-controlled measurements, 3% vs. 6% (p < .01). ConclusionsOne single duration-controlled injection thermodilution measurement is as accurate and repeatable as the mean of four phase-controlled measurements and is clinically feasible.

The effect of biventricular pacing on cardiac function after weaning from cardiopulmonary bypass in patients with reduced left ventricular function: A pressure–volume loop analysis

OBJECTIVE Patients with severely reduced left ventricular function undergoing coronary artery bypass grafting have increased complication rates. We hypothesized that temporary postoperative atrial synchronous biventricular pacing would improve left ventricular function after cardiopulmonary bypass. METHODS A left ventricular pressure-volume catheter was placed in 21 patients undergoing coronary artery bypass grafting (ejection fraction 29% +/- 5%). Pressure-volume loops were obtained after weaning from cardiopulmonary bypass with atrial synchronous biventricular, left ventricular, and right ventricular outflow tract pacing and atrial-only stimulation at 90 beats/min. RESULTS Steady-state systolic and preload-independent parameters were superior for atrial synchronous biventricular and left ventricular pacing and atrial-only pacing relative to atrial synchronous right ventricular outflow tract pacing (P < .05). Diastolic parameters, excepting maximum negative rate of left ventricular pressure change, were unaffected. No significant differences were observed between atrial synchronous biventricular and left ventricular pacing and atrial-only pacing. Systolic dyssynchrony was significantly lower for atrial synchronous biventricular pacing (21% +/- 5%), atrial synchronous left ventricular pacing (20% +/- 6%), and atrial-only pacing (20% +/- 6%) versus atrial synchronous right ventricular outflow tract pacing (25% +/- 7%, P < .05). Atrioventricular interval during atrial-only stimulation was positively correlated with difference in stroke work between atrial synchronous biventricular pacing and atrial-only pacing (r(2) = 0.78, P > .001). CONCLUSION Postoperative atrial synchronous biventricular and left ventricular pacing and atrial-only stimulation significantly improve systolic function relative to atrial synchronous right ventricular outflow tract pacing. If atrioventricular conduction is prolonged, atrial synchronous biventricular pacing is preferable to atrial-only pacing.

Surgical methods to reverse left ventricular remodeling in congestive heart failure.

In this review article, we describe the most common surgical procedures currently used to reverse or arrest remodeling of the left ventricle in patients with congestive heart failure (CHF). The selection of the appropriate operation in a patient is a complex decision-making process, rigorously based on pathophysiologic considerations. In this population, all factors affecting the surgical risk should be carefully evaluated preoperatively, and surgery should be recommended when definite benefits in survival and quality of life can be reasonably predicted. Quite often, patients with CHF require a combination of different procedures to address all the pathophysiologic components determining the clinical picture. In particular, in this review we describe the surgical restoration of the left ventricle, the isolated coronary artery bypass graft procedure, the correction of mitral regurgitation, diastolic support (from dynamic cardiomyoplasty to passive containment), and mechanical assist devices. Moreover, in the future, the role of surgery in the treatment of CHF will be strongly modified by the advent of gene therapy, cell therapy, and engineered artificial myocardial tissue.

Acute effects of beating heart coronary surgery on left ventricular performance.

BACKGROUND The increasing use of off-pump bypass grafting (OPCABG), requires an evaluation of its effects on left ventricular (LV) performance. METHODS In 8 patients with multivessel coronary disease who were undergoing to off-pump coronary artery bypass grafting, LV performance was analyzed from the pressure-volume (P-V) plane by the conductance catheter technique. Measurements were performed at base line, after the exposure of the vessels, after the application of the stabilization system, and at the end of the procedure. RESULTS No significant changes in heart rate, LV end-systolic volume, LV end-diastolic pressure, mean pulmonary artery, and mean systemic blood pressure were observed in the various stages of the procedure. Cardiac index decreased during left anterior descending coronary artery grafting after application of the stabilizer with a concomitant decrease in LV end-diastolic volume, together with decreases in LV peak negative -dP/dt and increases in tau, indicating an impairment of LV relaxation but without a change in preload recruitable stroke work, indicating preserved LV contractile state. Exposure of posterior and lateral vessels induced a decrease in cardiac index and preload recruitable stroke work without a decrease in LV preload, indicating a decrease in LV contractile state together with a decrease in peak -dP/dt and increase in tau, indicating an impairment in LV relaxation CONCLUSIONS Off-pump coronary artery bypass grafting can be performed without decreasing LV performance. Major cardiac displacement like that used for posterior and lateral exposure induces acutely significant decrease in LV contractile state.

PERFORMANCE OF A REAL-TIME DICROTIC NOTCH DETECTION AND PREDICTION ALGORITHM IN ARRHYTHMIC HUMAN AORTIC PRESSURE SIGNALS

A novel algorithm for real-time detection and prediction of the dicrotic notch from aortic pressure waves was evaluated in arrhythmic aortic pressure signals from heart failure patients. A simplified model of the arterial tree was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was detected at the first negative dip from the calculated flow, prediction of the notch was performed using a percentage of the decreasing flow. The performance of the real-time dicrotic notch detection algorithm (RTDND) was evaluated during severe arrhythmia from aortic pressure signals of 12 patients. The RTDND was able to detect the dicrotic notch in 98.1%. No false positive dicrotic notch identifications were observed. Prediction of the dicrotic notch was tested at 40%, 20%, and 0% of the decreasing calculated aortic flow. The mean time-delays to the notch were 68 ± 14 ms, 55 ± 12 ms, and 43 ± 8 ms, respectively. Given these small variability, intra-beat prediction of the dicrotic notch may be used for real-time intra-aortic balloon counterpulsation inflation timing.