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Proximal Isovelocity Surface Area Method for Diagnosing Isolated Pulmonary Vein Stenosis in a Case of Complete Atrioventricular Septal Defect With Increased Pulmonary Venous Blood Flow

Babu, Saravana MD, DM*; Gadhinglajkar, Shrinivas MD, PDCC*; Sreedhar, Rupa MD, PDCC*; Senniappan, Kirubanand MD, DM*; G. N., Chennakeshavallu MD, DM*; Dutta Baruah, Sudip MS, MCh

doi: 10.1213/XAA.0000000000000892
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From the Departments of *Anesthesia

Cardiothoracic and Vascular Surgery, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India.

Accepted for publication August 1, 2018.

Funding: None.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website.

Address correspondence to Shrinivas Gadhinglajkar, MD, PDCC, Department of Anesthesia, Sree Chitra Tirunal Institute for medical Sciences and Technology, Trivandrum 695011, India. Address e-mail to shri@sctimst.ac.in, drgadhinglajkar@gmail.com.

An 11-month-old male child (weight 6.7 kg and height 64 cm), a known case of complete balanced atrioventricular septal defect (AVSD), was scheduled for intracardiac repair. Preoperative transthoracic echocardiography examination revealed a large ostium primum atrial septal defect, a large inlet ventricular septal defect, mild left and right atrioventricular valve regurgitation, balanced AVSD, and normal biventricular systolic function. In the operating room, after induction of anesthesia, examination of the heart using a pediatric transesophageal echocardiography probe (IE33; Philips ultrasound, Bothell, WA) confirmed the preoperative transthoracic echocardiography findings. Additional observations were presence of flow turbulence in all the 4 pulmonary veins on color-flow Doppler analysis (Supplemental Digital Content 1, Video 1, http://links.lww.com/AACR/A219). Spectral Doppler interrogation of the individual pulmonary veins on both sides revealed a continuous pattern of high-velocity flow and nonexistence of atrial waveform (Figure 1A, B, C, D). The maximum velocity and peak pressure gradient across the right upper pulmonary vein (RUPV) were 214 cm/s and 18 mm Hg, respectively. Color-flow Doppler examination in the midesophageal RUPV view at a Nyquist limit of 50–60 cm/s revealed color aliasing and formation of proximal isovelocity surface area (PISA) at the entry point of RUPV to left atrium (LA) (Supplemental Digital Content 2, Video 2, http://links.lww.com/AACR/A220). The RUPV-LA junction was zoomed in, and the upper baseline of the Nyquist limit was adjusted to 35 cm/s for acquisition of an optimum hemispherical PISA shell. With the PISA radius of 0.30 cm (Figure 2) and pulmonary venous peak velocity of 214 cm/s, the area of RUPV at the LA junction derived using the PISA formula (2 × π × r2 × [aliasing velocity/maximum velocity]) was 0.093 cm2. Assuming the RUPV to be a circular structure, its diameter estimated from the area obtained by PISA method (circle area = 0.785 × [diameter]2; 0.093 = 0.785 × [diameter]2) was 3.44 mm, which was smaller than the normal size (6.52 mm) of this patient as predicted using an angiographically well-correlated formula ([0.08 × height {in cm}] + 1.4).1 Inspection of RUPV showed a circumferential fibrotic stricture at the RUPV-LA junction, and the direct anatomical site measurement of RUPV diameter by the surgeon was approximately 3.5 mm. A double-patch repair of AVSD was performed along with pericardial patch widening of the stenosed portion of the RUPV. Post-cardiopulmonary bypass (CPB) transesophageal echocardiography examination revealed no residual intracardiac defects and laminar flow across the right and left pulmonary veins (Supplemental Digital Content 3, Video 3, http://links.lww.com/AACR/A221). The peak gradient across the RUPV was reduced to 5 mm Hg (Figure 3). He had an uneventful postoperative period.

Figure 1.

Figure 1.

Figure 2.

Figure 2.

Figure 3.

Figure 3.

A written informed consent was obtained from patient’s relative for publication of this case report.

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DISCUSSION

An AVSD is a congenital cardiac disease associated with increased pulmonary blood flow, which produces rise in the systolic and diastolic flow velocities and nonappearance of atrial contraction wave resulting in continuous antegrade wave (CAW) on pulmonary venous Doppler flow profile.2 The CAW is also observed on pulmonary venous Doppler interrogation in the presence of pulmonary venous stenosis.3 Both of them coexisted in our patient, although the Doppler features of isolated RUPV stenosis were masked by those of the increased pulmonary venous flow characteristics of AVSD. An abnormal high-flow velocity (214 cm/s) at RUPV in comparison to other pulmonary veins and formation of PISA at RUPV-LA junction created a high index of suspicion for RUPV stenosis.

PISA, the flow convergence method uses the principle of conservation of mass to estimate the area of an orifice, is frequently used in valvular lesions and intracardiac shunts.4,5 However, its application for the measurement of orifice area in pulmonary venous stenosis is not reported to the best of our knowledge. We observed a series of concentric hemispherical shells with flow acceleration at the RUPV-LA junction. Normal dimensions of pulmonary veins vary among pediatric population depending on the body surface area. Use of nomograms incorporating height-based formulae is routine for the comparison of pulmonary venous diameters during angiographic studies.1 The pulmonary venous orifice area calculated by PISA method in our patient was smaller than the projected reference angiographic nomograms, indicating the presence of RUPV orifice stenosis. Timely detection of RUPV orifice stenosis in the pre-CPB period prompted the surgeon to undertake the corrective surgery in addition to the AVSD repair, which averted the second run of CPB.

The characteristic CAW of pulmonary venous Doppler flow immediately reverses after the closure of cardiac shunts with decrease in the systolic and diastolic waveforms and increase in atrial contraction waveform.6 If there is underlying pulmonary vein stenosis, the normalization of pulmonary venous Doppler waveform will not occur. It will present as deteriorating oxygenation and unilateral opacification of the involved lobe on chest x-ray in the postoperative period. In this case, the decrease in RUPV velocity likely occurred both due to RUPV repair and correction of AVSD. Hence, we recommend to examine the pulmonary veins for the reversal of CAW in the post-CPB period after the closure of cardiac shunts. Although the application of PISA for the calculation of pulmonary vein diameter is not a validated method of diagnosis, it is a novel and interesting application that would require further studies.

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DISCLOSURES

Name: Saravana Babu, MD, DM.

Contribution: This author helped conceive and design the case report, validate the data, and write and edit the manuscript.

Name: Shrinivas Gadhinglajkar, MD, PDCC.

Contribution: This author helped conceive the case report, and edit and write the manuscript.

Name: Rupa Sreedhar, MD, PDCC.

Contribution: This author helped conceive the case report, validate the data, and edit the manuscript.

Name: Kirubanand Senniappan, MD, DM.

Contribution: This author helped edit the manuscript.

Name: Chennakeshavallu G. N., MD, DM.

Contribution: This author helped edit and write the manuscript.

Name: Sudip Dutta Baruah, MS, MCh.

Contribution: This author helped edit the manuscript.

This manuscript was handled by: Kent H. Rehfeldt, MD.

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REFERENCES

1. Robida A. Diameters of pulmonary veins in normal children–an angiocardiographic study. Cardiovasc Intervent Radiol. 1989;12:307–309.
2. Chockalingam A, Dass S, Alagesan R, et al. Role of transthoracic Doppler pulmonary venous flow pattern in large atrial septal defects. Echocardiography. 2005;22:9–13.
3. Ha JW, Chung N, Yoon J, et al. Pulsed wave and color Doppler echocardiography and cardiac catheterization findings in bilateral pulmonary vein stenosis. J Am Soc Echocardiogr. 1998;11:393–396.
4. Enriquez-Sarano M, Miller FA Jr, Hayes SN, Bailey KR, Tajik AJ, Seward JB. Effective mitral regurgitant orifice area: clinical use and pitfalls of the proximal isovelocity surface area method. J Am Coll Cardiol. 1995;25:703–709.
5. Kurotobi S, Sano T, Matsushita T, et al. Quantitative, non-invasive assessment of ventricular septal defect shunt flow by measuring proximal isovelocity surface area on colour Doppler mapping. Heart. 1997;78:305–309.
6. Lin WW, Fu YC, Jan SL, et al. Immediate change in pulmonary venous flow pattern after deployment of occluder device for atrial septal defect. Echocardiography. 2009;26:452–458.

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