When the right atrial pressure (RAP) exceeds the left atrial pressure, right-to-left shunting can occur. Normally, the Valsalva maneuver is used to facilitate elevation of RAP. However, performing the Valsalva maneuver can be problematic in certain situations. The aim of this study was to test the hypothesis that the application of abdominal pressure would increase the pressure within the right atrium compared with the left atrium, making it an adequate alternative to the Valsalva maneuver. Twelve patients were prospectively evaluated during right-sided cardiac catheterization with the application of abdominal pressure as well as a Valsalva maneuver. RAP and left atrial pressure were measured simultaneously. In 11 patients, the mean RAP was lower than the mean pulmonary capillary wedge pressure at baseline. The mean RAP was significantly higher than the mean pulmonary capillary wedge pressure during abdominal compression (24.8 ± 9.9 vs 21.6 ± 8.8 mm Hg, p = 0.001). When the Valsalva maneuver was performed, mean RAP was also significantly higher than the mean pulmonary capillary wedge pressure (25.3 ± 10.9 vs 22.1 ± 10.3 mm Hg, p = 0.008). In conclusion, abdominal compression is similar to an optimal Valsalva maneuver for increasing RAP and thus the right-to-left pressure gradient. Performing abdominal compression provides a simple alternative to the Valsalva maneuver for creating a transient increase in RAP.
When the right atrial pressure (RAP) exceeds the left atrial pressure (LAP), right-to-left shunting can occur. Elevation of the RAP beyond the LAP helps facilitate the passage of agitated saline from the right to the left atrium in the case of a patent foramen ovale (PFO). The sensitivity of this technique is enhanced using maneuvers that cause transient elevation in the pressure gradient between the right and left atria and the possibility of a right-to-left shunt, such as with a Valsalva maneuver, which causes venous stasis and a reduction in cardiac preload. However, although partially feasible during transthoracic echocardiography (despite leading to a decrease in image quality), applying this maneuver in patients who undergo transesophageal echocardiography is often not applicable because patients are often sedated during this procedure. In experimental models, it has been shown that increasing abdominal pressure causes venous stasis, increasing RAP. Our hypothesis was that the application of abdominal pressure would increase the pressure within the right atrium compared with the left atrium.
Methods
We prospectively evaluated 12 patients, a total of 13 exams during right-sided cardiac catheterization. All patients were undergoing routine evaluation after cardiac transplantation, were in sinus rhythm, and had normal left ventricular ejection fractions. Hemodynamic measurements were taken while the patients were supine in the cardiac catheterization laboratory. Patients were given up to 2 mg of intravenous midazolam before the procedure for sedation if needed. A 7Fr Swan-Ganz catheter (Baxter Healthcare Corporation, Edwards Critical Care Division, Deerfield, Illinois) was introduced using the Seldinger technique through an internal jugular vein and positioned under fluoroscopic guidance in the pulmonary artery. Transducers were balanced by determining zero level at the midaxillary line. Consecutive standard measurement of RAP (from the proximal catheter port) and pulmonary capillary wedge pressure (PCWP; from the distal end of the catheter port) were obtained simultaneously using 2 transducers before, during, and after application of midabdominal compression in the range of 35 to 50 mm Hg. Investigators were previously trained in how to approximate abdominal compression of 35 mm Hg by measuring the effect of compression using a partially inflated sphygmomanometer, as previously described. The wedge position of the inflated Swan-Ganz catheter pulmonary artery balloon was verified by fluoroscopy and phasic changes in pressure waveforms. The values of PCWP were assessed at end-expiration with the balloon-tipped catheter at steady state with the patient in a supine position. Measurements were recorded at baseline, during abdominal compression, and during the Valsalva maneuver and were based on an average of 5 cardiac cycles. The study was approved by the institutional review board, and all patients gave informed consent.
Continuous variables are presented as mean ± SD and were compared using Student’s t tests if data followed a normal distribution and Wilcoxon’s rank-sum test if data were skewed. All tests were 2 sided, and p values <0.05 were considered statistically significant.
Results
The study population comprised 10 men (83%) with a mean age of 38 ± 12 years. Table 1 lists the results for the 13 studies performed. In 11 patients, the mean RAP was lower than the mean PCWP at baseline, the average mean RAP was 6.2 ± 2.1 mm Hg, and the average baseline mean PCWP was 9.6 ± 4.4 mm Hg. The mean RAP was significantly higher than the mean PCWP during abdominal compression (24.8 ± 9.9 vs 21.6 ± 8.8 mm Hg, p = 0.001), as represented in the example in Figure 1 . The mean gradient between RAP and PCWP during abdominal compression was 3 ± 2.7 mm Hg. The mean RAP was greater than the mean PCWP in 11 of the 13 patients during abdominal compression and equal between the 2 atria in the remaining 2 patients. None of the patients had lower mean RAP than mean PCWP during abdominal compression. When the Valsalva maneuver was performed, mean RAP was also significantly higher than the mean PCWP (25.3 ± 10.9 vs 22.1 ± 10.3 mm Hg, p = 0.008). During the Valsalva maneuver, mean RAP was greater than mean PCWP in 10 patients, equal in 1, and lower in 1. One patient was unable to perform the Valsalva maneuver.
| Study | Baseline | Abdominal Compression | Valsalva Maneuver | |||
|---|---|---|---|---|---|---|
| RAP (mm Hg) | PCWP (mm Hg) | RAP (mm Hg) | PCWP (mm Hg) | RAP (mm Hg) | PCWP (mm Hg) | |
| 1 | 8 | 6 | 26 | 21 | 21 | 15 |
| 2 | 4 | 9 | 19 | 15 | 20 | 12 |
| 3 | 6 | 9 | 28 | 28 | 23 | 18 |
| 4 | 2 | 5 | 8 | 7 | 5 | 5 |
| 5 | 4 | 9 | 25 | 23 | 28 | 26 |
| 6 | 9 | 3 | 25 | 20 | 38 | 30 |
| 7 | 6 | 8 | 38 | 36 | 38 | 34 |
| 8 | 8 | 14 | 18 | 18 | 16 | 20 |
| 9 | 4 | 8 | 18 | 14 | 19 | 16 |
| 10 | 7 | 19 | 24 | 22 | 23 | 21 |
| 11 | 8 | 15 | 48 | 38 | 45 | 43 |
| 12 | 7 | 12 | 27 | 25 | 27 | 25 |
| 13 | 7 | 8 | 18 | 14 | NA | NA |
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