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Regarding “The value of hemodynamic measurements by air plethysmography in diagnosing venous obstruction of the lower limb”
LETTERS TO THE EDITOR Regarding “The value of hemodynamic measurements by air plethysmography in diagnosing venous obstruction of the lower limb”
Christopher R. Lattimer, MBBS, FRCS, MS, FdIT, DIC, PhD Evi Kalodiki, MD, MA, PhD, DIC, FRCS
We congratulate the authors on their evaluation of air plethysmography (APG) in assessing venous obstruction of the leg.1 We are in full support of their conclusion that calf muscle pump function parameters of ejection fraction and residual volume fraction are unwarranted in diagnosing deep venous obstruction in any clinical practice. Why did the authors choose these tests for obstruction? Regarding the outflow fraction (OF), although it has long been considered a measure of outflow, as the name itself indicates, this has not been substantiated in a large clinical study before and after stenting.2 However, its value is well known. A reduced OF indicates venous fibrosis from deep venous thrombosis, irrespective of the presence of obstruction, as the authors agree. Therefore, correctly discrediting OF as a measure of obstruction should be made distinct from the value of OF in deep venous thrombosis diagnosis. In the conclusion, they state that “absolute volume changes or a different APG maneuver might be more informative.” In this respect, we would like to recommend gravitational filling and drainage testing using APG on a tilt table as performed originally by Allan in 1964.3 First, tilt-table angulations provide a controlled, artifact-free environment for quantifying volume changes. Second, the Trendelenburg position is a powerful maneuver for leg drainage. It is remarkable that this pioneering work of J. C. Allan has remained undiscovered for half a century. It is intuitive that the rate of reduction of calf volume on leg elevation may have something to do with the venous drainage, slower drainage being related to obstruction and rapid drainage being related to an unobstructed outflow. This can be quantified with the novel venous drainage index (VDI) of APG. Recently, three studies on validating the VDI have been published as abstracts. The first demonstrated that the inflation pressure of proximal obstruction with a thigh cuff correlated with a reduction in calf drainage rate and an increase in the undrained reserve volume.4 The second demonstrated a statistical improvement in the VDI after stenting of iliac vein lesions.5 The third, on a tilt table, defined a VDI cutoff point of 11 mL/s between healthy controls and post-thrombotic syndrome patients after a femoral vein thrombosis.6 While the authors seem hasty to confine APG to an experimental research laboratory, they may be missing a test of clinical importance. Given the numbers of patients with iliac vein lesions that are stented unnecessarily, because they demonstrate no clinical improvement after stenting, it may prove helpful to perform a drainage test beforehand. For example, it may not be wise to stent someone who has excellent gravitational drainage, but this needs further verification. Furthermore, the VDI test is the exact opposite of the clinically validated test for reflux, the venous filling index, both measured in milliliters per second. We may be premature in our positive conclusions regarding the value of the VDI. However, we recommend that APG deserves further consideration and that it not be dismissed in the way the authors have suggested on the basis of the inappropriate use of OF, ejection fraction, and residual volume fraction tests.
Department of Surgery and Cancer Imperial College London, United Kingdom
Josef Pflug Vascular Laboratory Ealing Hospital Middlesex, United Kingdom
West London Vascular and Interventional Centre Northwick Park Hospital Middlesex, United Kingdom Erika Mendoza, MD, PhD Venenpraxis Wunstorf, Germany George Geroulakos, MD, FRCS, DIC, PhD Josef Pflug Vascular Laboratory Ealing Hospital Middlesex, United Kingdom Department of Surgery and Cancer Imperial College London, United Kingdom West London Vascular and Interventional Centre Northwick Park Hospital Middlesex, United Kingdom
REFERENCES 1. Kurstjens RL, de Wolf MA, Alsadah SA, Arnoldussen CW, Strijkers RH, Toonder IM, et al. The value of hemodynamic measurements by air plethysmography in diagnosing venous obstruction of the lower limb. J Vasc Surg Venous Lymphat Disord 2016;4: 313-9. 2. Raju S, Kirk O, Davis M, Olivier J. Hemodynamics of “critical” venous stenosis and stent treatment. J Vasc Surg Venous Lymphat Disord 2014;2:52-9. 3. Allan JC. Volume changes in the lower limb in response to postural alterations and muscular exercise. S Afr J Surg 1964;2:75-90. 4. Lattimer CR, Doucet S, Kalodiki E, Azzam M, Ibegbuna V, Geroulakos G. Increasing thigh compression pressure correlates with a reduction in the venous drainage index of air-plethysmography. Phlebology 2015;30:699. 5. Lattimer CR, Kalodiki E, Azzam M, Schnatterbeck P, Geroulakos G. Gravitational venous drainage improves significantly after iliac venous stenting but this may result in faster venous filling. J Vasc Surg Venous Lymphat Disord 2016;4:137-8. 6. Lattimer CR, Mendoza E. Simultaneous air-plethysmography and duplex scanning on a tilt-table in assessing gravitational venous drainage. J Vasc Surg Venous Lymphat Disord 2016;4:151-2.
http://dx.doi.org/10.1016/j.jvsv.2016.03.009
537
Christopher R. Lattimer, MBBS, FRCS, MS, FdIT, DIC, PhD Evi Kalodiki, MD, MA, PhD, DIC, FRCS
We congratulate the authors on their evaluation of air plethysmography (APG) in assessing venous obstruction of the leg.1 We are in full support of their conclusion that calf muscle pump function parameters of ejection fraction and residual volume fraction are unwarranted in diagnosing deep venous obstruction in any clinical practice. Why did the authors choose these tests for obstruction? Regarding the outflow fraction (OF), although it has long been considered a measure of outflow, as the name itself indicates, this has not been substantiated in a large clinical study before and after stenting.2 However, its value is well known. A reduced OF indicates venous fibrosis from deep venous thrombosis, irrespective of the presence of obstruction, as the authors agree. Therefore, correctly discrediting OF as a measure of obstruction should be made distinct from the value of OF in deep venous thrombosis diagnosis. In the conclusion, they state that “absolute volume changes or a different APG maneuver might be more informative.” In this respect, we would like to recommend gravitational filling and drainage testing using APG on a tilt table as performed originally by Allan in 1964.3 First, tilt-table angulations provide a controlled, artifact-free environment for quantifying volume changes. Second, the Trendelenburg position is a powerful maneuver for leg drainage. It is remarkable that this pioneering work of J. C. Allan has remained undiscovered for half a century. It is intuitive that the rate of reduction of calf volume on leg elevation may have something to do with the venous drainage, slower drainage being related to obstruction and rapid drainage being related to an unobstructed outflow. This can be quantified with the novel venous drainage index (VDI) of APG. Recently, three studies on validating the VDI have been published as abstracts. The first demonstrated that the inflation pressure of proximal obstruction with a thigh cuff correlated with a reduction in calf drainage rate and an increase in the undrained reserve volume.4 The second demonstrated a statistical improvement in the VDI after stenting of iliac vein lesions.5 The third, on a tilt table, defined a VDI cutoff point of 11 mL/s between healthy controls and post-thrombotic syndrome patients after a femoral vein thrombosis.6 While the authors seem hasty to confine APG to an experimental research laboratory, they may be missing a test of clinical importance. Given the numbers of patients with iliac vein lesions that are stented unnecessarily, because they demonstrate no clinical improvement after stenting, it may prove helpful to perform a drainage test beforehand. For example, it may not be wise to stent someone who has excellent gravitational drainage, but this needs further verification. Furthermore, the VDI test is the exact opposite of the clinically validated test for reflux, the venous filling index, both measured in milliliters per second. We may be premature in our positive conclusions regarding the value of the VDI. However, we recommend that APG deserves further consideration and that it not be dismissed in the way the authors have suggested on the basis of the inappropriate use of OF, ejection fraction, and residual volume fraction tests.
Department of Surgery and Cancer Imperial College London, United Kingdom
Josef Pflug Vascular Laboratory Ealing Hospital Middlesex, United Kingdom
West London Vascular and Interventional Centre Northwick Park Hospital Middlesex, United Kingdom Erika Mendoza, MD, PhD Venenpraxis Wunstorf, Germany George Geroulakos, MD, FRCS, DIC, PhD Josef Pflug Vascular Laboratory Ealing Hospital Middlesex, United Kingdom Department of Surgery and Cancer Imperial College London, United Kingdom West London Vascular and Interventional Centre Northwick Park Hospital Middlesex, United Kingdom
REFERENCES 1. Kurstjens RL, de Wolf MA, Alsadah SA, Arnoldussen CW, Strijkers RH, Toonder IM, et al. The value of hemodynamic measurements by air plethysmography in diagnosing venous obstruction of the lower limb. J Vasc Surg Venous Lymphat Disord 2016;4: 313-9. 2. Raju S, Kirk O, Davis M, Olivier J. Hemodynamics of “critical” venous stenosis and stent treatment. J Vasc Surg Venous Lymphat Disord 2014;2:52-9. 3. Allan JC. Volume changes in the lower limb in response to postural alterations and muscular exercise. S Afr J Surg 1964;2:75-90. 4. Lattimer CR, Doucet S, Kalodiki E, Azzam M, Ibegbuna V, Geroulakos G. Increasing thigh compression pressure correlates with a reduction in the venous drainage index of air-plethysmography. Phlebology 2015;30:699. 5. Lattimer CR, Kalodiki E, Azzam M, Schnatterbeck P, Geroulakos G. Gravitational venous drainage improves significantly after iliac venous stenting but this may result in faster venous filling. J Vasc Surg Venous Lymphat Disord 2016;4:137-8. 6. Lattimer CR, Mendoza E. Simultaneous air-plethysmography and duplex scanning on a tilt-table in assessing gravitational venous drainage. J Vasc Surg Venous Lymphat Disord 2016;4:151-2.
http://dx.doi.org/10.1016/j.jvsv.2016.03.009
537