1/
Ventriculoarterial coupling (#VAC) determines the harms and benefits of hemodynamic therapies.
VAC describes cardiac efficiency, and offers a complementary perspective to CO, MAP and tissue perfusion.
Let’s try to understand it🧵
#FOAMcc #FOAMed #MedTwitter #CardioTwitter
Ventriculoarterial coupling (#VAC) determines the harms and benefits of hemodynamic therapies.
VAC describes cardiac efficiency, and offers a complementary perspective to CO, MAP and tissue perfusion.
Let’s try to understand it🧵
#FOAMcc #FOAMed #MedTwitter #CardioTwitter
2/
VAC is the matching afterload (Ea) to contractility (Ees) and reflect the heart's energy efficiency.
VAC can be understood using the analogy of riding a bicycle.
VAC is the matching afterload (Ea) to contractility (Ees) and reflect the heart's energy efficiency.
VAC can be understood using the analogy of riding a bicycle.
3/
The resistance in the pedals represent afterload (Ea). Your leg strength represent contractility (Ees).
With too⬆️resistance in the pedals, you spend a lot of energy without moving forward and eventually give up. This is analogous to poor VAC progressing into cardiac failure.
The resistance in the pedals represent afterload (Ea). Your leg strength represent contractility (Ees).
With too⬆️resistance in the pedals, you spend a lot of energy without moving forward and eventually give up. This is analogous to poor VAC progressing into cardiac failure.
4/
The optimal resistance (afterload, Ea) for you is determined by your personal leg strength (contractility, Ees)💪
By adjusting the gears, you can optimize the resistance to your personal strength.
This is how afterload is matched to contractility in VAC.
The optimal resistance (afterload, Ea) for you is determined by your personal leg strength (contractility, Ees)💪
By adjusting the gears, you can optimize the resistance to your personal strength.
This is how afterload is matched to contractility in VAC.
5/
By adjusting the gears, you can either oprimize for max performance or max efficiency.
Max performance represents your top speed⏩
Max efficiency minimizes energy wastage and determines how long and far you can ride before fatigue⏳
By adjusting the gears, you can either oprimize for max performance or max efficiency.
Max performance represents your top speed⏩
Max efficiency minimizes energy wastage and determines how long and far you can ride before fatigue⏳
6/
Back to the heart❤️:
Max performance occur when Ea/Ees-ratio ~ 1.
Max efficiency occur when Ea/Ees-ratio ~ 0.5.
Pathologic VAC occurs when Ea/Ees-ratio > 1.36.
If ignored, low efficiency from poor VAC can result in cardiac overload and failure.
Back to the heart❤️:
Max performance occur when Ea/Ees-ratio ~ 1.
Max efficiency occur when Ea/Ees-ratio ~ 0.5.
Pathologic VAC occurs when Ea/Ees-ratio > 1.36.
If ignored, low efficiency from poor VAC can result in cardiac overload and failure.
7/
Poor VAC can occur despite hypotension and low wall stress afterload🧐
VAC is poor in patients with ⬇️MAP after cardiac surgery...
...and in unresuscitated patient with septic shock.
doi.org/10.1097/CCM.00…
doi.org/10.1186/s13054…
Poor VAC can occur despite hypotension and low wall stress afterload🧐
VAC is poor in patients with ⬇️MAP after cardiac surgery...
...and in unresuscitated patient with septic shock.
doi.org/10.1097/CCM.00…
doi.org/10.1186/s13054…
8/
VAC is also poor in preload responsive patients and VAC improves after fluids if they were responsive.
Proposed mechanism:
⬇️SV causes vasoconstriction,⬆️Ea and poor VAC.
Each beat is inefficient, despite low afterload according to Laplace.
doi.org/10.1186/s12871…
VAC is also poor in preload responsive patients and VAC improves after fluids if they were responsive.
Proposed mechanism:
⬇️SV causes vasoconstriction,⬆️Ea and poor VAC.
Each beat is inefficient, despite low afterload according to Laplace.
doi.org/10.1186/s12871…
9/
Hemodynamic therapies affect VAC differently, so we the need to monitor VAC for hemodynamic optimization.
VAC can be assessed noninvasively using #EchoFirst and the iElastance-app.
However, it requires multiple measurements.
Hemodynamic therapies affect VAC differently, so we the need to monitor VAC for hemodynamic optimization.
VAC can be assessed noninvasively using #EchoFirst and the iElastance-app.
However, it requires multiple measurements.
10/
As classical #EchoFirst parameters are load dependent, perhaps these parameters reflect VAC.
This is certainly true for LVEF...:
...and for TAPSE and RVFAC:
doi.org/10.1097/000005…
doi.org/10.1093/ehjci/…
As classical #EchoFirst parameters are load dependent, perhaps these parameters reflect VAC.
This is certainly true for LVEF...:
...and for TAPSE and RVFAC:
doi.org/10.1097/000005…
doi.org/10.1093/ehjci/…
11/
As low systolic function indicates poor VAC, automated #EchoFirst in real-time is very exciting for monitoring VAC. Also for #POCUS users:
@SindreOlaisendoi.org/10.1093/ehjci/…
As low systolic function indicates poor VAC, automated #EchoFirst in real-time is very exciting for monitoring VAC. Also for #POCUS users:
@SindreOlaisendoi.org/10.1093/ehjci/…
12/
In sum, VAC reflects cardiac efficiency and provides a complementary perspective to cardiac performance (CO, MAP, DO2).
It would be very interesting to see if optimizing VAC can reduce cardiac complications after surgery or #CriticalCare #ICU.
In sum, VAC reflects cardiac efficiency and provides a complementary perspective to cardiac performance (CO, MAP, DO2).
It would be very interesting to see if optimizing VAC can reduce cardiac complications after surgery or #CriticalCare #ICU.
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