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Table of Contents
ORIGINAL ARTICLE  
Year : 2012  |  Volume : 15  |  Issue : 2  |  Page : 118-121
Occluding the pulmonary artery to improve detection of patent foramen ovale during ventricular assist device placement


Department of Anesthesia, Jewish Hospital and St. Mary's Healthcare and University of Louisville, 200 Abraham Flexner Way, Louisville, KY, USA

Click here for correspondence address and email

Date of Web Publication16-Apr-2012
 

   Abstract 

Unrecognized patent foramen ovale (PFO) in patients after left ventricular assist device (VAD) placement could cause significant hypoxemia and paradoxical embolism. We aim to improve the techniques for PFO detection in this patient population before left ventricular device initiation. We evaluated the effects of main pulmonary artery occlusion on patients' hemodynamic and detection of PFO by transesophageal echocardiography (TEE). We compared between the standard and pulmonary artery occlusion technique. Sixty-two patients with ASA physical status class IV were studied. They presented with end-stage heart failure for left VAD placement. All patients received both Valsava maneuver and occlusion of their pulmonary arteries to assess their influence on detection of PFO. Occlusion of the main pulmonary artery consistently increased right atrial to left atrial pressure gradient. The PFO detection rate using TEE was significantly improved from 0% to 10% by this maneuver compared with the Valsava maneuver. Occlusion of the main pulmonary artery is a simple and effective method to improve PFO detection by TEE before left VAD initiation.

Keywords: Congenital heart disease, circulatory assist devices, echocardiography, septal defects

How to cite this article:
Huang J, Bouvette MJ. Occluding the pulmonary artery to improve detection of patent foramen ovale during ventricular assist device placement. Ann Card Anaesth 2012;15:118-21

How to cite this URL:
Huang J, Bouvette MJ. Occluding the pulmonary artery to improve detection of patent foramen ovale during ventricular assist device placement. Ann Card Anaesth [serial online] 2012 [cited 2019 Oct 19];15:118-21. Available from: http://www.annals.in/text.asp?2012/15/2/118/95074



   Introduction Top


Patients who have end-stage heart failure are often left with no other operative option than either a heart transplant or ventricular assist devices (VAD). VADs can serve as either a destination therapy or a bridge to transplant. Patent foramen ovale (PFO) is a probe patent or flap valve competent foramen ovale, allowing blood to flow only from the right to the left atrium in most cases. In congestive heart failure, the left atrium pressure is usually much higher than the right atrial pressure, and PFO stays closed even tighter that routine proactive maneuvers can fail to detect shunting. [1] However, unloading the left ventricle by left VADs (LVAD) will decrease the left atrial pressure (LAP) and, to a much lesser extent, the right atrial pressure (RAP). [2] This hemodynamic consequence might cause right to left atrial shunting if a PFO exists, which could result in significant hypoxemia or paradoxical embolism from air or emboli with ensuing stroke or myocardial infarction. Little can be more devastating to both the patient and the physician with a VAD operation than a well-performed technical operation derailed by an undiagnosed PFO.

To alleviate this unwanted discovery, a reproduction of the decrease in LAP prior to the implantation will allow a previously unrecognized PFO to be identified and repaired. Transesophageal echocardiography (TEE) with bubble study after standard provocative maneuvers is considered the golden standard for PFO detection. The diagnostic accuracy is only 86% in the general preoperative population. [3] To best replicate the decrease in LAP after LVAD initiation, we previously reported a technique in which we prepared the patient for bypass and, just prior to its institution, we clamped the pulmonary artery (PA) while visualizing the interatrial septum using TEE. As the septum shifts direction toward the left atrium, we perform a bubble study. [4] This technique seems superior to the traditional bubble study test because, frequently, the release of the Valsalva maneuver does not generate a large enough change in interatrial pressures to overcome the significantly elevated LAP in these end-stage patients. [5] The aim of this study is to assess the efficacy and possible complications associated with this technique in a larger patient population undergoing LVADs placement.


   Materials and Methods Top


Patients

Between May 2004 and June 2008, 62 consecutive patients who underwent the LVAD procedure in our center were enrolled in this study.

Techniques

After institutional review board approval, informed consent was obtained from all subjects. Arterial line, central venous line and  Swan-Ganz catheter More Details were placed in all patients. After standard anesthesia induction and intubation, a multiplane TEE probe was inserted and a comprehensive TEE exam was performed by a senior echocardiographer according to published guidelines and recommendations. [5],[6] After the chest was opened, to detect any interatrial shunting, initially, color flow Doppler with an aliasing velocity of 33 cm/s was performed in Midesophageal four-chamber and bicaval views. Thereafter, bubble contrast studies using 10 ml agitated saline administered through a central venous catheter positioned near the right atrium with the concurrent release of a Valsalva held at airway pressure of 50 cm H 2 O (standard maneuver) were repeated in both the views. This technique was repeated three times for each patient. A PFO was defined by the appearance of microbubbles in the left atrium within three cardiac cycles on all three attempts and shunting by color flow Doppler.

Normal surgical preparations of the patient for cardiopulmonary bypass (CPB) via a median sternotomy occurred. Once ready to initiate the CPB, the surgeon manually started occluding the main pulmonary artery to decrease the LAP, which manifested on TEE by bowing of the interatrial septum toward the left atrium. A bubble study with agitated saline as described above was then performed to visualize any interartial shunting. Midesophageal four-chamber and bicaval views were used with angles adjusted until a clear view of the interatrial septum and both atria was achieved. This study was repeated three times while allowing hemodynamic recovery in between. On average, each test lasted about 15 s. If nonreversible hemodynamic deterioration occurred, CPB would be initiated. If this revealed a PFO, bicaval cannulation for CPB, surgical inspection of the interatrial septum and repair were performed. A standard bubble study was repeated after CPB while the chest was still open. The remainder of the operation was completed with standard techniques. All patients were followed for desaturation and received either a transthoracic echocardiography or TEE to evaluate PFO postoperatively.

Statistical analysis

Assuming PFO detection rate with pulmonary artery occlusion technique at 25%, standard technique in VAD patients at 5%, α=0.05, 1-β=0.80, the sample size was determined to be 58 patients for a two-sided test. Comparison of difference between the standard and the pulmonary artery occlusion techniques on PFO detection was calculated from Fisher's exact test.


   Results Top


Sixty-two patients (42 men, 20 women; mean age, 53.3 ± 11.2 years; range 20-72 years) who underwent left VAD procedure at our center were included in the study. The cause of heart failure was ischemic cardiomyopathy in 31 patients (50%), viral cardiomyopathy in four patients (6%), drug-induced cardiomyopathy in three patients (4%), amyloid cardiomyopathy in one patient (1%) and idiopathic cardiomyopathy in 23 patients (37%).

Partial occlusion of the pulmonary artery allowed a significant decrease in both systemic and pulmonary pressures, with a dramatic elevation in central venous pressure (CVP) by increasing the afterload of the right ventricle. Different forces to occlude the PA had to be applied in individual patients to achieve adequate interatrial septum bowing. At the time when septal bowing was observed, CVP was invariably higher than pulmonary diastolic pressure [Figure 1]. Release of the PA occlusion predictably reversed the hemodynamic changes in all patients without the necessity of immediate CPB. In a 41-year-old female during LVAD placement, PA pressure was 42/31 mmHg and CVP was 28 mmHg, with cardiac output of 2.4 L/min before the maneuver. CVP increased to 41 mmHg while PA pressure decreased to 25/16 mmHg after PA occlusion when a PFO was detected.
Figure 1: Illustration of the effects of pulmonary artery occlusion on pressures in different cardiac chambers with resultant patent foramen ovale opening

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Preoperative assessment with Valsava maneuvers did not show bowing of the interatrial septum (defined as interatrial septum displacement of at least 5 mm measured by the echocardiographer) toward the left atrium and a PFO in any patient (0%). Occlusion of PA caused bowing of the interatrail septum toward the left atrium in all patients (100%) and detected PFOs in six patients (10%) [Figure 2]. The PA occlusion technique significantly improved PFO detection in this patient population (P=0.0275). Initiation of LVAD invariably caused bowing of the interatrial septum toward the left atrium. Postoperative evaluation revealed no undetected PFO in any patient. No patient required a second operation for PFO repair.
Figure 2: Microbubbles of agitated saline still passed from the right atrium to the left atrium when the occlusion of the pulmonary artery was slowly released

Click here to view



   Discussion Top


A PFO is a probe patent or flap valve competent foramen ovale and is caused by incomplete anatomic fusion of septum primum and septum secundum. Under normal physiologic conditions, LAP is slightly higher than RAP, and there is no right to left shunt, and the PFO remains clinically benign. Because the LAP and RAP are reasonably close in a normal patient, the standard Valsava maneuver usually reveals any PFO. However, in congestive heart failure patients, the LAP is usually much higher than RAP and, resultantly, the PFO remain closed despite the standard Valsava maneuvers. After LVAD initiation, LAP is decreased significantly with respect to the RAP, and this reversal of pressure gradient may cause blood or air to shunt from the right to the left atrium through a PFO. [1],[7],[8]

The standard maneuver for PFO detection consists of release of positive intrathoracic pressure, which increases the right atrial filling and the RAP. However, this small increase of RAP is often not sufficient to overcome the exaggerated LAP in congestive heart failure patients. As demonstrated in this and the study by Liao et al., [6] the standard Valsava maneuvers before initiation of the LVAD failed to produce consistent and significant reversal of the relative pressure gradients between the right and the left atrium, which did not allow diagnosis of a high percentage of PFOs. Occlusion of PA, which increased the pressure gradient from right to left atrium, did reveal these PFOs. This maneuver is consistent and effective regardless of the LAP, because the surgeon can adjust the needed PA occlusion to achieve the necessary increase in RAP and drop in LAP as evidenced by bowing of the interatrail septum toward the left atrium.

Occlusion of the PA increased our PFO detection rate in this patient population from 0/62 to 6/62. No new PFOs were demonstrated postoperatively, giving a negative predictive value of 100%. Our PFO incidence rate in LVAD patients was 10%, which is less than the 25% rate in the general population. This could be due to either this specific patient population or the small size of our sample. False-positive results are likely when transpulmonary or iatrogenic shunting occurs. False-negative concerns arise from inadequate changes between left and right atrial pressures by PA occlusion and the inherently limited sensitivity of bubble studies.

Shunting after LVAD initiation can cause significant hypoxemia, exacerbate a preexisting hypoxemic condition or paradoxical emboli and stroke. The severity of hypoxemia is unpredictable, and is determined by the amount of shunting, which can be affected by the size of PFO, the pressure gradient between RAP and LAP and the redistribution of shunt flow. The atrial pressure gradient may vary with different preload conditions, and this explains the characteristics of intermittent hypoxemia caused by a PFO in LVAD patients. [1],[7] The treatment options for PFO after LVAD placement include both surgical and percutaneous closure. [1],[7] Surgical closure carries the risks of bleeding, right ventricular dysfunction and multiple organ failure. The percutaneous approach sometimes proves to be a low risk and effective alternative in these patients.

The limitations of our study are the small size of this study and that our end point outcome is a clinically significant PFO. We did not evaluate other outcomes with this technique. Further, because of the three-dimensional properties of the interatrial septum, two-dimensional evaluation of septal bowing might be misleading. Three-dimensional echocardiography might provide additional information and guide accurate application of this technique.

In summary, we demonstrated that occlusion of the PA effectively improved the detection of PFO compared with the standard evaluation techniques in patients with end-stage heart failure. Further study is needed to evaluate whether this result could be generalized to other patient populations.

 
   References Top

1.Liao KK, Miller L, Toher C, Ormaza S, Herrington CS, Bittner HB, et al. Timing of transesophageal echocardiography in diagnosing patent foramen ovale in patients supported with left ventricular assist device. Ann Thorac Surg 2003;75:1624-6.  Back to cited text no. 1
[PUBMED]    
2.Nakatani S, Thomas JD, Savage RM, Vargo RL, Smedira NG, McCarthy PM. Prediction of right ventricular dysfunction after left ventricular assist device implantation. Circulation 1996;94(9 Suppl):2216-21.  Back to cited text no. 2
    
3.Sukernick M, Mets B, Benett-Guerrero E. Patent foramen ovale and its significance in the preoperative period. Anesth Analg 2001;93:1137-46.  Back to cited text no. 3
    
4.Majd RE, Kavarana MN, Bouvette M, Dowling RD. Improved technique to diagnose a patent foramen ovale during left ventricular assist device insertion. Ann Thorac Surg 2006;82:1917-9.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  
5.Chumnanvej S, Wood MJ, MacGillivray TE, Melo MF. Perioperative echocardiographic examination for ventricular assist device implantation. Anesth Analg 2007;105:583-601.  Back to cited text no. 5
[PUBMED]  [FULLTEXT]  
6.Shanewise JS, Cheung AT, Aronson S, Stewart WJ, Weiss RL, Mark JB, et al. ASE/SCA guidelines for performing a comprehensive intraoperative multiplane transesophageal echocardiography examination: Recommendations of the American Society of Echocardiography Council for Intraoperative Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force for Certification in Perioperative Transesophageal Echocardiography. Anesth Analg 1999;89:870-84.  Back to cited text no. 6
[PUBMED]  [FULLTEXT]  
7.Kavarana MN, Rahman FA, Recto MR, Dowling RD. Transcatheter closure of patent foramen ovale after left ventricular assist device implantation: Intraoperative decision making. J Heart Lung Transplant 2005;24:1445.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.Srinivas CV, Collins N, Borger MA, Horlick E, Murphy PM. Hypoxemia complicating LVAD insertion: Noval application of the Amplatzer PFO occlusion device. J Card Surg 2007;22:156-8.  Back to cited text no. 8
[PUBMED]  [FULLTEXT]  

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Correspondence Address:
Jiapeng Huang
200 Abraham Flexner Way, Louisville, KY 40202
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-9784.95074

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