Results: The flow in DCM exhibited qualitative differences due to the weakness of the formed vortices in the large LV chamber. DCM and healthy subjects show significant volumetric differences; these also reflect inflow properties like the vortex formation time, energy dissipation, and sub-volumes describing flow transit. Proper normalization permitted to define purely fluid dynamics indicators that are not influenced by volumetric measures. Conclusion: Cardiac fluid mechanics can be evaluated by a combination of imaging and numerical simulation. This pilot study on pathological changes in LV blood motion identified intraventricular flow indicators based on pure fluid mechanics that could potentially be integrated with existing indicators of cardiac mechanics in the evaluation of disease progression.

Background QRS narrowing following cardiac resynchronization therapy with biventricular (BiV) or left ventricular (LV) pacing is likely affected by patient‐specific conduction characteristics (PR, qLV, LV‐paced propagation interval), making a universal programming strategy likely ineffective. We tested these factors using a novel, device‐based algorithm (SyncAV) that automatically adjusts paced atrioventricular delay (default or programmable offset) according to intrinsic atrioventricular conduction.Methods and ResultsSeventy‐five patients undergoing cardiac resynchronization therapy (age 66±11 years; 65% male; 32% with ischemic cardiomyopathy; LV ejection fraction 28±8%; QRS duration 162±16 ms) with intact atrioventricular conduction (PR interval 194±34, range 128–300 ms), left bundle branch block, and optimized LV lead position were studied at implant. QRS duration (QRSd) reduction was compared for the following pacing configurations: nominal simultaneous BiV (Mode I: paced/sensed atrioventricular delay=140/110 ms), BiV+SyncAV with 50 ms offset (Mode II), BiV+SyncAV with offset that minimized QRSd (Mode III), or LV‐only pacing+SyncAV with 50 ms offset (Mode IV). The intrinsic QRSd (162±16 ms) was reduced to 142±17 ms (−11.8%) by Mode I, 136±14 ms (−15.6%) by Mode IV, and 132±13 ms (−17.8%) by Mode II. Mode III yielded the shortest overall QRSd (123±12 ms, −23.9% [P<0.001 versus all modes]) and was the only configuration without QRSd prolongation in any patient. QRS narrowing occurred regardless of QRSd, PR, or LV‐paced intervals, or underlying ischemic disease.ConclusionsPost‐implant electrical optimization in already well‐selected patients with left bundle branch block and optimized LV lead position is facilitated by patient‐tailored BiV pacing adjusted to intrinsic atrioventricular timing using an automatic device–based algorithm.

Visualization of the three-dimensional flow within the Right Ventricle (RV) is a challenging issue due to the fully three-dimensional geometry of the ventricular cavity. To date proper characterization and quantification of the RV flow still remains incomplete, and techniques that can be easily applied to current medical imaging are scarce. A method for simulating the highly complex, multi directional flow within the RV is presented by coupling 4D echocardiography imaging with numerical simulations based on the Immersed Boundaries Method (IBM). A novel formulation for accurately computing the space-time distribution of the blood residence time inside the cavity is introduced. Results showed an initial compact vortex forming past the tricuspid orifice at early diastole that quickly breaks into a weakly turbulent flow pattern and rearranges, during systole, into a peculiar stream-wise vortex spinning out towards the pulmonary orifice. This arrangement is maintained when the Ejection Fraction (EF) is reduced from 58 to 32%. The average blood transit time is found to scale almost inversely proportional to the EF. A careful analysis of the residence time permitted to assess the relative significance of the different flow components (from the direct flow, with a residence time less than one heartbeat, to the residual volume, that stagnates in the ventricle) and their distribution in space.

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