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Estimation of cardiac output in patients with congestive heart failure by analysis of right ventricular pressure
Mustafa Karamanoglu1, Tom Bennett, Marcus Ståhlberg
1NT&D Research, Medtronic Inc, Minneapolis, Minnesota, USA. mustafa.karamanoglu@medtronic.com
Insights
Estimating cardiac output (CO) from right ventricular pressure waveforms using an implantable device shows promise for managing congestive heart failure (CHF). This method accurately tracks CO changes during exercise, aiding treatment decisions.
Area of Science:
- Cardiology
- Biomedical Engineering
- Hemodynamics
Background:
- Cardiac output (CO) is crucial for assessing hemodynamics in congestive heart failure (CHF).
- Estimating CO from right ventricular (RV) pressure waveforms is a potential non-invasive approach.
- A pulse contour algorithm considering RV outflow tract characteristic impedance was investigated.
Purpose of the Study:
- To test the hypothesis that CO can be estimated from RV pressure waveforms in CHF patients.
- To assess the accuracy of an implantable hemodynamic monitor algorithm for CO estimation.
- To evaluate the algorithm's performance during exercise.
Main Methods:
- Retrospective analysis of RV pressure waveforms and Fick CO in 12 CHF patients during exercise.
- Prospective study of 4 patients with an implantable cardiac defibrillator (ICD) implementing the CO algorithm.
- Comparison of ICD-estimated CO with direct Fick CO measurements during a two-stage bicycle exercise test.
Main Results:
- RV outflow tract characteristic impedance remained unchanged during exercise.
- Algorithm-derived CO estimates showed strong correlation with Fick CO (R(2) = 0.92).
- The algorithm effectively tracked changes in Fick CO (R(2) = 0.73) with a limit of agreement of 1.7 L/min.
Conclusions:
- Analysis of RV pressure waveforms via implantable hemodynamic monitors can estimate CO.
- This technology may assist in guiding CHF patient treatment.
- Continuous hemodynamic monitoring offers a valuable tool for managing heart failure.
Background:
Cardiac output (CO) is an important determinant of the hemodynamic state in patients with congestive heart failure (CHF). We tested the hypothesis that CO can be estimated from the right ventricular (RV) pressure waveform in CHF patients using a pulse contour cardiac output algorithm that considers constant but patient specific RV outflow tract characteristic impedance.
Method:
In 12 patients with CHF, breath-by-breath Fick CO and RV pressure waveforms were recorded utilizing an implantable hemodynamic monitor during a bicycle exercise protocol. These data were analyzed retrospectively to assess changes in characteristic impedance of the RV outflow tract during exercise. Four patients that were implanted with an implantable cardiac defibrillator (ICD) implementing the algorithm were studied prospectively. During a two staged sub-maximal bicycle exercise test conducted at 4 and 16 weeks of implant, COs measured by direct Fick technique and estimated by the ICD were recorded and compared.
Results:
At rest the total pulmonary arterial resistance and the characteristic impedance were 675 ± 345 and 48 ± 18 dyn.s.cm(-5), respectively. During sub-maximal exercise, the total pulmonary arterial resistance decreased (Δ 91 ± 159 dyn.s.cm(-5), p < 0.05) but the characteristic impedance was unaffected (Δ 3 ± 9 dyn.s.cm(-5), NS). The algorithm derived cardiac output estimates correlated with Fick CO (7.6 ± 2.5 L/min, R(2) = 0.92) with a limit of agreement of 1.7 L/min and tracked changes in Fick CO (R(2) = 0.73).
Conclusions:
The analysis of right ventricular pressure waveforms continuously recorded by an implantable hemodynamic monitor provides an estimate of CO and may prove useful in guiding treatment in patients with CHF.
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