Effect of Next Generation Pulsatile Mechanical Circulatory Support on Cardiac Mechanics: The PULSE Trial.

OBJECTIVES: To describe hemodynamic effects of iVAC2L mechanical circulatory support (MCS). BACKGROUND: MCS is increasingly used in the context of high-risk percutaneous coronary intervention (PCI). The effect of the pulsatile iVAC2L MCS on left ventricular loading conditions and myocardial oxygen consumption (MVO2) is unknown. METHODS: This prospective single-arm two-center study included 29 patients who underwent high-risk PCI with iVAC2L MCS using simultaneous invasive pulmonary pressure monitoring and left ventricular pressure-volume analysis. Hemodynamic recordings were performed during steady state conditions with MCS off and on before and after PCI. Pressure-volume variations were analyzed to denote responders and non-responders. RESULTS: The mean age was 74 (IQR: 70-81) years and the mean SYNTAX score was 31 ± 8.3. Left ventricular unloading with iVAC2L MCS was demonstrated in 22 out of 27 patients with complete PV studies. Patients with moderate or severe mitral regurgitation or presenting with acute coronary syndrome (ACS) had higher filling pressures and volumes and were most responsive to iVAC2L unloading (9/10 patients with moderate or severe MR and 11/11 patients with ACS). Pulsatile MCS activation reduced MAP (-4%), SBP (-9%), ESP (-11%), ESV (-15%) and EDV (-4%) among responders but not among non-responders. Responders experienced significant reductions in afterload (Ea: -19%) with increases in stroke volume (+11%) and cardiac output (+11%). CONCLUSIONS: Pulsatile iVAC2L MCS in patients with advanced coronary artery disease at high to prohibitive operative risk resulted in LV unloading and reduced myocardial oxygen consumption particularly in patients with ACS or significant MR with higher filling pressures at baseline. CLINICAL TRIAL REGISTRATION: NCT03200990.

Invasive Real Time Biventricular Pressure-Volume Loops to Monitor Dynamic Changes in Cardiac Mechanoenergetics During Structural Heart Interventions: Design and Rationale of a Prospective Single-Center Study.

Background: Transcatheter valvular interventions affect cardiac and hemodynamic physiology by changing ventricular (un-)loading and metabolic demand as reflected by cardiac mechanoenergetics. Real-time quantifications of these changes are scarce. Pressure-volume loop (PVL) monitoring appraises both load-dependent and load-independent compounds of cardiac physiology including myocardial work, ventricular unloading, and ventricular-vascular interactions. The primary objective is to describe changes in physiology induced by transcatheter valvular interventions using periprocedural invasive biventricular PVL monitoring. The study hypothesizes transcatheter valve interventions modify cardiac mechanoenergetics that translate into improved functional status at 1-month and 1-year follow-up. Methods: In this single-center prospective study, invasive PVL analysis is performed in patients undergoing transcatheter aortic valve replacement or tricuspid or mitral transcatheter edge-to-edge repair. Clinical follow-up is per standard of care at 1 and 12 months. This study aims to include 75 transcatheter aortic valve replacement patients and 41 patients in both transcatheter edge-to-edge repair cohorts. Results: The primary outcome is the periprocedural change in stroke work, potential energy, and pressure-volume area (mmHg mL-1). The secondary outcomes comprise changes in a myriad of parameters obtained by PVL measurements, including ventricular volumes and pressures and the end-systolic elastance-effective arterial elastance ratio as a reflection of ventricular-vascular coupling. A secondary endpoint associates these periprocedural changes in cardiac mechanoenergetics with functional status at 1 month and 1 year. Conclusions: This prospective study aims to elucidate the fundamental changes in cardiac and hemodynamic physiology during contemporary transcatheter valvular interventions.

Impact of coronary artery disease on contractile function and ventricular-arterial coupling during exercise: Simultaneous assessment of left-ventricular pressure-volume and coronary pressure and flow during cardiac catheterization.

Coronary artery disease (CAD) can adversely affect left ventricular (LV) performance during exercise by impairment of contractile function in the presence of increasing afterload. By performing invasive measures of LV pressure-volume and coronary pressure and flow during exercise, we sought to accurately measure this with comparison to the control group. Sixteen patients, with CCS class >II angina and CAD underwent invasive simultaneous measurement of left ventricular pressure-volume and coronary pressure and flow velocity during cardiac catheterization. Measurements performed at rest were compared with peak exercise using bicycle ergometry. The LV contractile function was measured invasively using the end-systolic pressure-volume relationship, a load independent marker of contractile function (Ees). Vascular afterload forces were derived from the ratio of LV end-systolic pressure to stroke volume to generate arterial elastance (Ea). These were combined to assess cardiovascular performance (ventricular-arterial [VA] coupling ratio [Ea/Ees]). Eleven patients demonstrated flow-limiting (FL) CAD (hyperemic Pd/Pa <0.80; ST-segment depression on exercise); five patients without flow-limiting (NFL) CAD served as the control group. Exercise in the presence of FL CAD was associated impairment of Ees, increased Ea, and deterioration of VA coupling. In the control cohort, exercise was associated with increased Ees and improved VA coupling. The backward compression wave energy directly correlated with the magnitude contraction as measured by dP/dTmax (r = 0.88, p = 0.004). This study demonstrates that in the presence of flow-limiting CAD, exercise to maximal effort can lead to impairment of LV contractile function and a deterioration in VA coupling compared to a control cohort.

Physiological Impact of Afterload Reduction on Cardiac Mechanics and Coronary Hemodynamics Following Isosorbide Dinitrate Administration in Ischemic Heart Disease.

Understanding the cardiac-coronary interaction is fundamental to developing treatment strategies for ischemic heart disease. We sought to examine the impact of afterload reduction following isosorbide dinitrate (ISDN) administration on LV properties and coronary hemodynamics to further our understanding of the cardiac-coronary interaction. Novel methodology enabled real-time simultaneous acquisition and analysis of coronary and LV hemodynamics in vivo using coronary pressure-flow wires (used to derive coronary wave energies) and LV pressure-volume loop assessment. ISDN administration resulted in afterload reduction, reduced myocardial demand, and increased mechanical efficiency (all P<0.01). Correlations were demonstrated between the forward compression wave (FCW) and arterial elastance (r=0.6) following ISDN. In the presence of minimal microvascular resistance, coronary blood flow velocity exhibited an inverse relationship with LV elastance. In summary this study demonstrated a reduction in myocardial demand with ISDN, an inverse relationship between coronary blood flow velocity and LV contraction-relaxation and a direct correlation between FCW and arterial elastance. The pressure volume-loop and corresponding parameters b The pressure volume loop before (solid line) and after (broken line) Isosorbide dintrate.

Invasive Cardiomechanics During Transcatheter Edge-to-Edge Repair for Massive Tricuspid Regurgitation Using Biventricular Pressure-Volume Loop Monitoring.

Invasive pressure-volume loop analysis allows direct monitoring of changing intraventricular cardiac mechanics during structural heart interventions. Our aim was to illustrate changes in right and left ventricular mechanics during transcatheter edge-to-edge tricuspid repair for severe tricuspid regurgitation. (Level of Difficulty: Advanced.).

Determination of cardiac output from pulse pressure contour during intra-aortic balloon pumping in patients with low ejection fraction.

Evaluation of a new Windkessel model based pulse contour method (WKflow) to calculate stroke volume in patients undergoing intra-aortic balloon pumping (IABP). Preload changes were induced by vena cava occlusions (VCO) in twelve patients undergoing cardiac surgery to vary stroke volume (SV), which was measured by left ventricular conductance volume method (SVlv) and WKflow (SVwf). Twelve VCO series were carried out during IABP assist at a 1:2 ratio and seven VCO series were performed with IABP switched off. Additionally, SVwf was evaluated during nine episodes of severe arrhythmia. VCO's produced marked changes in SV over 10-20 beats. 198 paired data sets of SVlv and SVwf were obtained. Bland-Altman analysis for the difference between SVlv and SVwf during IABP in 1:2 mode showed a bias (accuracy) of 1.04 ± 3.99 ml, precision 10.9% and limits of agreement (LOA) of - 6.94 to 9.02 ml. Without IABP bias was 0.48 ± 4.36 ml, precision 11.6% and LOA of - 8.24 to 9.20 ml. After one thermodilution calibration of SVwf per patient, during IABP the accuracy improved to 0.14 ± 3.07 ml, precision to 8.3% and LOA to - 6.00 to + 6.28 ml. Without IABP the accuracy improved to 0.01 ± 2.71 ml, precision to 7.5% and LOA to - 5.41 to + 5.43 ml. Changes in SVlv and SVwf were directionally concordant in response to VCO's and during severe arrhythmia. (R2 = 0.868). The SVwf and SVlv methods are interchangeable with respect to measuring absolute stroke volume as well as tracking changes in stroke volume. The precision of the non-calibrated WKflow method is about 10% which improved to 7.5% after one calibration per patient.

Invasive left ventricle pressure-volume analysis: overview and practical clinical implications.

Ventricular pressure-volume (PV) analysis is the reference method for the study of cardiac mechanics. Advances in calibration algorithms and measuring techniques brought new perspectives for its application in different research and clinical settings. Simultaneous PV measurement in the heart chambers offers unique insights into mechanical cardiac efficiency. Beat to beat invasive PV monitoring can be instrumental in the understanding and management of heart failure, valvular heart disease, and mechanical cardiac support. This review focuses on intra cardiac left ventricular PV analysis principles, interpretation of signals, and potential clinical applications.

New-generation mechanical circulatory support during high-risk PCI: a cross-sectional analysis.

AIMS: The aim of the study was to establish the value of new-generation mechanical circulatory support (MCS) devices such as HeartMate PHP, Impella CP and PulseCath iVAC2. METHODS AND RESULTS: We retrospectively analysed all consecutive elective high-risk PCI procedures performed in the Erasmus Medical Center (2011-2018) in order to compare MCS protected and unprotected patients. The primary endpoint was a composite of procedure-related adverse events including death (<24 hours), cardiac arrest, need for vasopressors, rescue MCS, endotracheal intubation and limb ischaemia with need for surgery. Secondary endpoints included 30-day survival. A total of 198 elective high-risk PCI patients were included (69 [35%] MCS protected, 129 [65%] MCS unprotected). When compared with unprotected patients, MCS protected patients had a significantly worse left ventricular ejection fraction (LVEF) (25±10 vs 33±8%, p<0.01) and higher SYNTAX I score (33±11 vs 24±8, p<0.01). The primary endpoint occurred in 26 (20%) of the unprotected patients and in 6 (9%) of the MCS protected patients (OR 0.38, 95% CI: 0.15-0.97, p=0.04). Patients under 75 years of age, with a SYNTAX I score above 32 and with an LVEF below 30% showed most potential benefit from MCS. Survival during the first 24 hours after the procedure and at 30 days was significantly higher in MCS protected patients (100% vs 95%, p=0.04 at 24 hours, and 98% vs 87%, OR 10.32, 95% CI: 1.34-79.31, p=0.006 at 30 days). CONCLUSIONS: In a consecutive real-world cohort of high-risk PCI patients, protection with new-generation MCS resulted in better procedural outcomes despite worse EF and more complex coronary artery disease at baseline. Larger prospective studies are needed to confirm these findings.

Real-time left ventricular pressure-volume loops during percutaneous mitral valve repair with the MitraClip system.

BACKGROUND: Percutaneous mitral valve repair with the MitraClip device has emerged as an alternative to surgery for treating severe mitral regurgitation. However, its effects on left ventricular loading conditions and contractility have not been investigated yet. METHODS AND RESULTS: Pressure-volume loops were recorded throughout the MitraClip procedure using conductance catheter in 33 patients (mean age, 78±10 years) with functional (45%), degenerative (48%), or mixed (6%) mitral regurgitation. Percutaneous mitral valve repair increased end-systolic wall stress (WSES; from [median] 184 mm Hg [interquartile range (IQR), 140-200 mm Hg] to 209 mm Hg [IQR, 176-232 mm Hg]; P=0.001) and decreased end-diastolic WS (WSED; from 48 mm Hg [IQR, 28-58 mm Hg] to 34 mm Hg [IQR, 21-46 mm Hg]; P=0.005), whereas the end-systolic pressure-volume relationship was not significantly affected. Conversely, cardiac index increased (from 2.6 L·min(-1)·m(-2) [IQR, 2.2-3.0 L·min(-1)·m(-2)] to 3.2 L·min(-1)·m(-2) [IQR, 2.6-3.8 L·min(-1)·m(-2)]; P<0.001) and mean pulmonary capillary wedge pressure decreased (from 15 mm Hg [IQR, 12-20 mm Hg] to 12 mm Hg [IQR, 10-13 mm Hg]; P<0.001). Although changes in WSES were not correlated with changes in cardiac index, changes in WSED correlated significantly with changes in mean pulmonary capillary wedge pressure (r=0.63, P<0.001). Total mechanical energy assessed by the pressure-volume area remained unchanged, resulting in a more favorable index of forward output (cardiac index) to mechanical energy (pressure-volume area) after mitral valve repair. On follow-up (153±94 days), New York Heart Association functional class was reduced from 2.9±0.6 to 1.9±0.5 (P<0.001) at 3 months, and echocardiographic follow-up documented a stepwise reduction in end-diastolic volume (from 147 mL [IQR, 95-191 mL] to 127 mL [IQR, 82-202 mL]; P=0.036). CONCLUSIONS: Percutaneous mitral valve repair improves hemodynamic profiles and induces reverse left ventricular remodeling by reducing left ventricular preload while preserving contractility. In nonsurgical candidates with compromised left ventricular function, MitraClip therapy could be considered an alternative to surgical mitral valve repair.

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.

Coherent averaging improves the evaluation of left ventricular dyssynchrony by conductance catheter.

OBJECTIVE: Coherent averaging is a technique to recover the response to repetitively applied stimuli when that response is embedded in random noise. We derived novel indices for left ventricular dyssynchrony estimation from volume-catheter signals using coherent averaging procedure: mechanical dyssynchrony (DYSCoh) internal flow fraction (IFFCoh) and mechanical dispersion (DISPCoh). The percentage power of non-repetitive components in the volume signals (ResTotAvg) was also estimated. The aims of the study were to evaluate the indices, characterizing repetitive and non-recurrent components of the conductance-volume signals, and to assess the ability of these indices to detect the changes in dyssynchrony induced by biventricular pacing (BIV). METHODS: We compared the results obtained in 20 heart failure patients indicated to BIV (HF Group) during spontaneous conduction with the results from 12 patients with preserved ventricular function (non-HF Group), and with those obtained during BIV. RESULTS: DISPCoh and ResTotAvg were significantly different in HF compared to non-HF group, and identified HF patients with high accuracy (area under curve at ROC analysis > 0.8). These indices also demonstrated significant differences after BIV (p = 0.047 and p = 0.037 respectively) and their baseline values correlated with the acute increase of stroke volume (r = 0.64 and r = 0.78, both with p < 0.005). CONCLUSIONS: Coherent averaging-based indices permit independent quantification and differentiation of repetitive components of ventricular dyssynchrony from non-recurrent mechanical non-uniformities, which seem associated with HF and conduction disturbances. These indices identified HF patients with high accuracy, and were able to describe the reversal of dyssynchrony caused by BIV and to predict the acute hemodynamic improvement.

Acute effects of His bundle pacing versus left ventricular and right ventricular pacing on left ventricular function.

Dual-chamber pacing with His bundle pacing has theoretical advantages over conventional right ventricular (RV) apical pacing. We compared indexes of left ventricular (LV) function during acute dual-chamber pacing from the His bundle and other RV and LV pacing sites. Twelve patients (6 men; 63 +/- 11 years) with a standard indication for electrophysiologic study were included. Average QRS duration was 100 +/- 19 ms. Ejection fraction was 48 +/- 15%. A pressure-volume catheter was positioned in the left ventricle through the femoral arterial access. Pressure-volume loops were collected during atrial (AAI) and dual-chamber overdrive pacing at 82 +/- 15 beats/min after 2 minutes of hemodynamic stabilization. Ventricular pacing catheter position was randomized between the RV apex, RV septal, and free wall portions of the outflow tract, LV free wall, and His bundle. His bundle capture was verified from surface electrocardiographic morphometry using standard criteria. Atrioventricular delay was set to the P wave-His duration -10 ms to minimize the effects of fusion (96 +/- 22 ms). LV only pacing, but not His pacing, resulted in improved stroke work and stroke volume compared with alternate site RV pacing. No changes in +dP/dt, LV end-systolic pressure. LV end-diastolic pressure, or cycle efficiency, were observed between RV pacing sites. In conclusion, acute His bundle pacing did not improve LV function compared with alternate site RV pacing and may be inferior to LV pacing.

Implantation of an elastic ring at equator of the left ventricle influences cardiac mechanics in experimental acute ventricular dysfunction.

OBJECTIVES: We hypothesize that the implantation of an endoventricular elastic ring at the left ventricle (LV) equatorial site will positively affect the cardiac mechanics in an experimental model of acute LV dysfunction. BACKGROUND: Changes in the elastic properties of LV occur in the dilated and failing heart, contributing to overall cardiac mechanical dysfunction. No interventions are as yet specifically designed to improve LV elasticity in failing hearts. METHODS: Acute LV enlargement and dysfunction was induced in 13 healthy sheep via the insertion of a large Dacron patch into the lateral wall. In 6 of these sheep, a customized elastic ring was implanted at the inner surface of the LV equator (ring group), and the remaining 7 served as control subjects (dysfunction group). Systolic and diastolic function was evaluated using echocardiography and pressure-volume (P-V) analysis. RESULTS: In the ring group, both the maximum rate of pressure increase and the slope of end-systolic P-V relationship were significantly different from those without ring (1,718 +/- 726 vs. 1,049 +/- 269 and 1.25 +/- 0.30 vs. 0.88 +/- 0.19; both p < 0.05). Preload recruitable stroke work changed even more prominently (33 +/- 11 vs. 17 +/- 5; p = 0.005), along with stroke volume, ejection fraction, and stroke work. Although ring implantation had no effect on end-diastolic P-V relationship, it positively affected the active component of diastole: the maximum rate of pressure decrease declined significantly (p = 0.037). The time constant of relaxation tended to decrease (37 +/- 8 vs. 44 +/- 6; p = 0.088). CONCLUSIONS: Improving the elastic component of the LV at its equatorial site substantially augments contractility and early relaxation in acute systodiastolic LV dysfunction.

Cardiac output derived from left ventricular pressure during conductance catheter evaluations: an extended Modelflow method.

OBJECTIVE: The Modelflow method computes cardiac output (CO) from arterial pressure (CO-MFao) by simulating a non-linear three-element Windkessel model of aortic input impedance. We present a novel technique to apply the Modelflow method to the left ventricular pressure (Plv) signal, to obtain an estimation of CO (CO-MFlv). METHODS: We extended the model by simulating the aortic valve as a resistance placed in series to the characteristic impedance. In our model the valve resistance is infinite in diastole, while it has a patient related value during systole. Twenty one patients with heart failure were studied with a combined pressure-conductance catheter positioned in the left ventricle and a micromanometer in the aorta. CO changes were induced during temporary sequential atrio-biventricular pacing with different atrio-ventricular and inter-ventricular intervals. After a single calibration we compared CO-MFlv with CO-MFao (516 measurement series) and with CO estimated by the conductance catheter volume technique (CO-cond) (267 series). RESULTS: CO ranged from 2.42 to 7.59 l/min with an overall mean of 4.36 (1.38) l/min. Comparing the two Modelflow methods, the bias was -0.04 (0.36) l/min, with limits of agreement of -0.77 and 0.70 l/min, and a coefficient of variation of 8.4%. Of the 516 changes in CO from baseline values, 112 were greater than 0.5 l/min and 110 of these (98%) were scored in the same direction by both methods. For comparisons between CO-MFlv and CO-cond the bias was -0.10 (0.49), with limits of agreement of -1.12 and 0.90 l/min, and a coefficient of variation of 12.5%. CONCLUSIONS: Cardiac output estimates by the modelflow method from aortic pressure and left ventricular pressure are interchangeable in patients without mitral and aortic abnormalities. After an initial calibration, CO-MFlv presents near zero bias and an adequate precision.

Ventricular pacing lead location alters systemic hemodynamics and left ventricular function in patients with and without reduced ejection fraction.

OBJECTIVES: We compared left ventricular (LV) systolic and diastolic function during right ventricular (RV), LV, and biventricular (BiV) pacing in patients with narrow QRS duration with and without LV dysfunction. BACKGROUND: The optimal RV pacing lead location for patients with a standard indication for ventricular pacing remains controversial. METHODS: Left ventricular pressure and volume data were determined via conductance catheter during electrophysiology study in 31 patients divided into groups with ejection fraction (EF) > or =40% (n = 17) or EF <40% (n = 14). QRS duration was 91 +/- 18 versus 106 +/- 25 ms, respectively (p = NS). Hemodynamic data were recorded during atrial and dual chamber pacing from the RV apex, RV free wall, RV septum, LV free wall, and BiV. RESULTS: In patients with EF > or =40%, RV pacing at 1 or more sites, but not LV free wall or BiV pacing, significantly (p < 0.05) impaired cardiac output (CO), stroke work (SW), EF, and LV relaxation compared with atrial overdrive pacing. Right ventricular pacing also impaired hemodynamics and LV function in patients with EF <40%. However, LV and BiV pacing increased CO, SW, EF, and LV +dP/dt(MAX) in patients with LV dysfunction. Left ventricular and BiV pacing enhanced an index of global LV cycle efficiency in patients with depressed EF. The detrimental hemodynamic effects of RV pacing were attenuated by selecting the optimal RV pacing site. CONCLUSIONS: Right ventricular pacing worsens LV function in patients with and without LV dysfunction unless the RV pacing site is optimized. Left ventricular and BiV pacing preserve LV function in patients with EF >40% and improve function in patients with EF <40% despite no clinical indication for BiV pacing.

Automatic intraaortic balloon pump timing using an intrabeat dicrotic notch prediction algorithm.

PURPOSE: The efficacy of intraaortic balloon counterpulsation (IABP) during arrhythmic episodes is questionable. A novel algorithm for intrabeat prediction of the dicrotic notch was used for real time IABP inflation timing control. DESCRIPTION: A windkessel model algorithm was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was predicted using a percentage of calculated peak flow. Automatic inflation timing was set at intrabeat predicted dicrotic notch and was combined with automatic IAB deflation. EVALUATION: Prophylactic IABP was applied in 27 patients with low ejection fraction (< 35%) undergoing cardiac surgery. Analysis of IABP at a 1:4 ratio revealed that IAB inflation occurred at a mean of 0.6 +/- 5 ms from the dicrotic notch. In all patients accurate automatic timing at a 1:1 assist ratio was performed. Seventeen patients had episodes of severe arrhythmia, the novel IABP inflation algorithm accurately assisted 318 of 320 arrhythmic beats at a 1:1 ratio. CONCLUSIONS: The novel real-time intrabeat IABP inflation timing algorithm performed accurately in all patients during both regular rhythms and severe arrhythmia, allowing fully automatic intrabeat IABP timing.

Beat-to-beat effects of intraaortic balloon pump timing on left ventricular performance in patients with low ejection fraction.

BACKGROUND: Intraaortic balloon counterpulsation (IABP) timing errors during arrhythmia may result in afterload increases which may negatively influence left ventricular (LV) ejection and LV mechanical dyssynchrony. The aim of our study was to determine beat-to-beat effects of properly timed IABP, premature IAB inflation, and late IAB deflation on LV performance and LV mechanical dyssynchrony in heart failure patients undergoing cardiac surgery. METHODS: In 15 patients, LV pressure-volume relations and LV dyssynchrony were measured by conductance volume catheter. Properly timed IABP was evaluated at a 1:1 assist ratio within a 10 seconds time-span. Premature IAB inflation and late IAB deflation were evaluated at a 1:4 assist ratio. RESULTS: Properly timed 1:1 IABP acutely decreased LV end-systolic volume by 6.1% (p < 0.0001) and LV end-systolic pressure by 17.5% (p < 0.0001) due to decreased aortic impedance. Stroke volume (SV) increased by 14% (p < 0.0001), which correlated markedly with a decrease of LV mechanical dyssynchrony (p < 0.0001). The largest SV increases occurred in patients with lowest contractile state. Premature IAB inflation decreased SV by 20% (p < 0.0001) due to abrupt increase of LV afterload during late ejection. Late IAB deflation increased SV and stroke work by 18% (p < 0.0001) and 16% (p < 0.01) respectively, due to increased afterload during early ejection and decreased afterload during late ejection. CONCLUSIONS: Left ventricular performance during IABP is causally related to changes in LV afterload, and the timing of these changes in relation to contraction or relaxation phases, to LV mechanical dyssynchrony and to contractile state.

Acute decrease of left ventricular mechanical dyssynchrony and improvement of contractile state and energy efficiency after left ventricular restoration.

OBJECTIVE: Surgical left ventricular restoration by means of endoventricular patch aneurysmectomy in patients with postinfarction aneurysm should result in acute improved left ventricular performance by decreasing mechanical dyssynchrony and increasing energy efficiency. METHODS: Nine patients with left ventricular postinfarction aneurysm were studied intraoperatively before and after ventricular restoration with a conductance volume catheter to analyze pressure-volume relationships, energy efficiency, and mechanical dyssynchrony. The end-systolic elastance was used as a load-independent index of contractile state. Left ventricular energy efficiency was calculated from stroke work and total pressure-volume area. Segmental volume changes perpendicular to the long axis were used to calculate mechanical dyssynchrony. Statistical analysis was performed with the paired t test and least-squares linear regression. RESULTS: Endoventricular patch aneurysmectomy reduced end-diastolic volume by 37% (P < .001), with unchanged stroke volume. Systolic function improved, as derived from increased +dP/dt(max), by 42% (P < .03), peak ejection rate by 28% (P < .02), and ejection fraction by 16% (P < .0002). Early diastolic function improved, as shown by reduction of -dP/dt(max) by 34% (P < .006) and shortened tau by 30% (P < .001). Left ventricular end-systolic elastance increased from 1.2 +/- 0.6 to 2.2 +/- 1 mm Hg/mL (P < .001). Left ventricular energy efficiency increased by 36% (P < .002). Left ventricular mechanical dyssynchrony decreased during systole by 33% (P < .001) and during diastole by 20% (P < .005). CONCLUSIONS: Left ventricular restoration induced acute improvements in contractile state, energy efficiency, and relaxation, together with a decrease in left ventricular mechanical dyssynchrony.