Tan W, Small A, Gallotti R, Moore J, Aboulhosn J.Int J Cardiol. 2020 Nov 13:S0167-5273(20)34081-X. doi: 10.1016/j.ijcard.2020.11.007. Online ahead of print.PMID: 33189798
Take Home Points:
- A higher central venous pressure (CVP) is required to drive pulmonary blood flow in the Fontan circulation, although chronically elevated CVP is associated with long-term Fontan complications.
- Peripheral venous pressure (PVP) has previously been shown to be a relatively robust non-invasive surrogate for CVP in pediatric Fontan patients.
- This study of adult Fontan patients showed a PVP measurement cutoff 14 mmHg was associated with 100 % sensitivity and 55 % specificity for detecting elevated Fontan pressure.
- PVP measurement may be a useful screening tool to identify high-risk Fontan patients with elevated CVP, with reassurance for those with a PVP less than 14 mmHg, and consideration of further evaluation indicated for those with elevated PVP.
Commentary from Dr. Timothy Roberts (Melbourne, Australia), section editor of ACHD Journal Watch: Patients with a Fontan circulation lack a subpulmonary ventricle and require a higher central venous pressure (CVP) to drive pulmonary blood flow. The long-term consequences of higher CVP can include liver cirrhosis and protein losing enteropathy, and mortality has been reported to be higher amongst those with a high CVP compared to those with lower CVP. Pulmonary artery pressure cannot be estimated non-invasively by traditional means in the Fontan circulation. Peripheral venous pressure (PVP) has been demonstrated to be a good surrogate for CVP in patients with acquired heart disease, while studies in pediatric Fontan patients have reported correlation between PVP and CVP. The current study aimed to compare PVP and CVP in adult Fontan patients undergoing cardiac catheterization, with the hypothesis that correlation between these measurements would be reproducible and robust, providing a non-invasive technique to estimate CVP in the outpatient setting.
This was a single-centre, prospective, cross-sectional study of adult Fontan patients undergoing clinically indicated cardiac catheterization. All adult patients (age 18 years) were included, and those with a known stenosis or obstruction of either the Fontan pathway or an upper extremity vein were excluded. A total of 43 cases were included. Catheterisation was performed under general anaesthetic. A peripheral intravenous line was placed in an upper extremity vein. Central venous pressure was measured at the superior vena cava level using a 5F – 7F wedge pressure catheter. Equipment was meticulously zeroed prior to measurements, and catheter location confirmed with fluoroscopy. Peripheral venous pressure was measured immediately after CVP measurement by transferring the same pressure transducer, or by using pressure tubing attached to a 3-way stopcock that was attached to the pressure transducer. The peripheral IV catheter was positioned at the level of the mid-axillary line. Both CVP and PVP measurements were recorded with an Edwards TruWave pressure transducer. Linear regression and a Bland-Altman plot analysis for differences were performed. Receiver operator characteristic (ROC) curve for PVP was created, using CVP of 14 mmHg or higher as a cutoff.
Table 1 demonstrates baseline demographics and patient characteristics in those undergoing cardiac catheterization. Mean age was 30.7 years, and 24 years post original Fontan surgery.
Mean CVP was 17.3 mmHg (SD 4.7 mmHg, range 9 – 30 mmHg), and mean PVP was 18.4 mmHg (SD 5 mmHg, range 9 – 35 mmHg). PVP was strongly correlated to CVP (figure 1):
Bland-Altman plot of PVP and CVP showed that PVP overestimated CVP by a mean of 1.2 mmHg (95% CI 0.47 – 1.9 mmHg) with limits of agreement between CVP and PVR from -5.2 to +2.8 mmHg:
PVP measurement cutoff 14 mmHg was associated with 100 % sensitivity and 55 % specificity for detecting elevated Fontan pressures. This corresponded to a 100 % negative predictive value and 84 % positive predictive value for the identification of elevated invasive Fontan pressures.
This study has found a very strong correlation between PVP and CVP in an older cohort of Fontan patients with more comorbidities and higher Fontan pressures than several other previous studies. PVP measurement may be a useful screening tool to identify high-risk Fontan patients with elevated CVP, with reassurance for those with a PVP less than 14 mmHg, and consideration of further evaluation suggested for those with elevated PVP. An important caveat to the extrapolation of these findings to the outpatient setting is the data arising from intubated and sedated patients; study in awake patients is clearly required before PVP measurement can be routinely recommended in Fontan patients.