Background-Transcatheter aortic valve implantation (TAVI) is

TAVI-induced new LBBB occurs in almost 40% of patients, almost all before hospital discharge. It occurs three times more frequently after MCS than after ES valve implantation and has a twofold lower tendency to resolve during follow-up. Persistent LBBB is associated with a higher mortality.

AimsThe maximum rate of left ventricular (LV) pressure rise (dP/dt max ) has been used to assess the acute haemodynamic effect of cardiac resynchronization therapy (CRT). We tested the hypothesis that LV dP/dt max predicts long-term clinical outcome after initiation of CRT. Methods and resultsThis was a retrospective observational multicentre study in 285 patients in whom dP/dt max was measured invasively following implantation of a CRT device. The minimum required follow-up was 1 year. We analysed the relationship between dP/dt max and time to the composite endpoint, consisting of all-cause mortality, heart transplantation (HTX), or LV assist device (LVAD) implantation within the first year of CRT. Thirty-four events occurred after a mean followup of 160 days (range 21 -359). Patients with an event had lower dP/dt max than patients without an event both at baseline (705 + 194 vs. 800 + 222 mmHg/s, P ¼ 0.018) and during CRT (894 + 224 vs. 985 + 244 mmHg/s, P ¼ 0.033), but the acute increase in dP/dt max was similar in patients with and without an event (190 + 133 vs. 185 + 115 mmHg/s, P ¼ n.s.). Left ventricular dP/dt max -level at baseline and during CRT both predicted the clinical outcome after adjustment for gender, aetiology and New York Heart Association class: hazard ratio (HR) 0.791 [95% confidence interval (CI) 0.658-0.950, P ¼ 0.012] and HR 0.846 (95% CI 0.723-0.991, P ¼ 0.038), respectively. ConclusionLeft ventricular dP/dt max measured at baseline and during CRT are predictors of 1-year survival free from all-cause mortality, HTX, or LVAD implantation, but the acute improvement in dP/dt max is not correlated to clinical outcome.--

AimsEchocardiography and tomographic imaging have documented dynamic changes in aortic stenosis (AS) geometry and severity during both the cardiac cycle and stress-induced increases in cardiac output. However, corresponding pressure gradient vs. flow relationships have not been described.Methods and resultsWe recruited 16 routine transcatheter aortic valve implantations (TAVI’s) for graded dobutamine infusions both before and after implantation; 0.014″ pressure wires in the aorta and left ventricle (LV) continuously measured the transvalvular pressure gradient (ΔP) while a pulmonary artery catheter regularly assessed cardiac output by thermodilution. Before TAVI, ΔP did not display a consistent relationship with transvalvular flow (Q). Neither linear resistor (median R2 0.16) nor quadratic orifice (median R2 < 0.01) models at rest predicted stress observations; the severely stenotic valve behaved like a combination. The unitless ratio of aortic to left ventricular pressures during systolic ejection under stress conditions correlated best with post-TAVI flow improvement. After TAVI, a highly linear relationship (median R2 0.96) indicated a valid valve resistance.ConclusionPressure loss vs. flow curves offer a fundamental fluid dynamic synthesis for describing aortic valve pathophysiology. Severe AS does not consistently behave like an orifice (as suggested by Gorlin) or a resistor, whereas TAVI devices behave like a pure resistor. During peak dobutamine, the ratio of aortic to left ventricular pressures during systolic ejection provides a ‘fractional flow reserve’ of the aortic valve that closely approximates the complex, changing fluid dynamics. Because resting assessment cannot reliably predict stress haemodynamics, ‘valvular fractional flow’ warrants study to explain exertional symptoms in patients with only moderate AS at rest.

Background-The relative contribution of electromechanical synchronization and ventricular filling to the optimal hemodynamic effect in cardiac resynchronization therapy (CRT) during adjustment of stimulation-timings is incompletely understood. We investigated whether optimal hemodynamic effect in CRT requires collision of pacing-induced and intrinsic activation waves and optimal filling of the left ventricle (LV). Methods and Results-CRT was performed in dogs with chronic left bundle-branch block (n=8) or atrioventricular (AV) block (n=6) through atrial (A), right ventricular (RV) apex, and LV-basolateral pacing. A 100 randomized combinations of A-LV/A-RV intervals were tested. Total activation time (TAT) was calculated from >100 contact mapping electrodes. Mechanical interventricular dyssynchrony was determined as the time delay between upslopes of LV and RV pressure curves. Settings providing an increase in LVdP/dt max (maximal rate of rise of left ventricular pressure) of ≥90% of the maximum LVdP/dt max value were defined as optimal (CRT opt ). Filling was assessed by changes in LV end-diastolic volume (EDV; conductance catheter technique). In all hearts, CRT opt was observed during multiple settings, providing an average LVdP/dt max increase of ≈15%. In AV-block hearts, CRT opt exclusively depended on interventricular-interval and not on AVinterval. In left bundle-branch block hearts, CRT opt occurred at A-LV intervals that allowed fusion of LV-pacing-derived activation with right bundle-derived activation. In all animals, CRT opt occurred at settings resulting in the largest decrease in TAT and mechanical interventricular dyssynchrony, whereas LV EDV hardly changed. Conclusions-In left bundle-branch block and AV-block hearts, optimal hemodynamic effect of CRT depends on optimal interplay between pacing-induced and intrinsic activation waves and the corresponding mechanical resynchronization rather than filling.

In this review, the physiological rationale for atrioventricular and interventricular delay optimization of cardiac resynchronization therapy is discussed including the influence of exercise and long-term cardiac resynchronization therapy. The broad spectrum of both invasive and non-invasive optimization methods is reviewed with critical appraisal of the literature. Although the spectrum of both invasive and non-invasive optimization methods is broad, no single method can be recommend for standard practice as large-scale studies using hard endpoints are lacking. Current efforts mainly investigate optimization during resting conditions; however, there is a need to develop automated algorithms to implement dynamic optimization in order to adapt to physiological alterations during exercise and after anatomical remodeling.

BackgroundContrast-enhanced ultrasound (CEUS) has recently been proposed as a minimally- invasive, alternative method for blood volume measurement. This study aims at comparing the accuracy of CEUS and the classical thermodilution techniques for volume assessment in an in-vitro set-up.MethodsThe in-vitro set-up consisted of a variable network between an inflow and outflow tube and a roller pump. The inflow and outflow tubes were insonified with an ultrasound array transducer and a thermistor was placed in each tube. Indicator dilution curves were made by injecting indicator which consisted of an ultrasound-contrast-agent diluted in ice-cold saline. Both acoustic intensity- and thermo-dilution curves were used to calculate the indicator mean transit time between the inflow and outflow tube. The volumes were derived by multiplying the estimated mean transit time by the flow rate. We compared the volumes measured by CEUS with the true volumes of the variable network and those measured by thermodilution by Bland-Altman and intraclass-correlation analysis.ResultsThe measurements by CEUS and thermodilution showed a very strong correlation (rs = 0.94) with a modest volume underestimation by CEUS of −40 ± 28 mL and an overestimation of 84 ± 62 mL by thermodilution compared with the true volumes. Both CEUS and thermodilution showed a high statistically significant correlation with the true volume (rs = 0.97 (95% CI, 0.95 - 0.98; P<0.0001) and rs = 0.96 (95% CI, 0.94 - 0.98; P<0.0001, respectively).ConclusionsCEUS volume estimation provides a strong correlation with both the true volumes in-vitro and volume estimation by thermodilution. It may therefore represent an interesting alternative to the standard, invasive thermodilution technique.

This technique for LV endocardial lead implantation is an alternative for failed CS and superior transseptal attempts using standard techniques and equipment. It is also applicable for pacing sites that are more easily reached from a femoral approach.