Development of pulmonary hypertension after placement of a ventriculoatrial shunt

Ventriculo-atrial shunt. Comparison of an ultrasound-guided peel-away technique versus conventional technique in the management of normal pressure hydrocephalus: A retrospective cohort

Background:

Normal pressure hydrocephalus (NPH) is a common neurodegenerative syndrome among the elderly characterized by ventriculomegaly and the classic triad of symmetric gait disturbance, cognitive decline and urinary incontinence. To date, the only effective treatment is a cerebrospinal fluid shunting procedure that can either be ventriculo-atrial, ventriculo-peritoneal, or lumbo-peritoneal shunt. The conventional ventriculo-atrial shunt uses venodissection, whereas the peel-away is a percutaneous ultrasound (US)-guided technique that shows some advantages over conventional technique. We sought to compare perioperative complication rates, mean operating time and clinical outcomes for both techniques in NPH patients at our institution.

Methods:

A retrospective cohort-type analytical study was conducted, using clinical record data of patients diagnosed with NPH and treated at our center from January 2009 to September 2019. Parameters to be compared include: Perioperative complication rates, intraoperative bleeding, mortality, and mean operating time. Perioperative complication rates are those device-related such as shunt infection, dysfunction, and those associated with the procedure. Complications are further classified in immediate (occurring during the first inpatient stay), early (within the first 30 days of surgery), and late (after day 30 of surgery).

Results:

A total of 123 patients underwent ventriculo-atrial shunt. Eighty-two patients (67%) underwent conventional venodissection technique and 41 patients (33%) underwent a peel-away technique. Immediate complications were 3 (3.6%) and 0 for conventional and peel-away groups, respectively. Early complications were 0 and 1 (2.4%) for conventional and peel-away groups, respectively. Late complications were 5 (6.1%) and 2 (4.9%) for conventional and peel-away groups, respectively. Mean operating time was lower in the peel-away group (P = 0.0000) and mortality was 0 for both groups.

Conclusion:

Ventriculo-atrial shunt is an effective procedure for patients with NPH. When comparing the conventional venodissection technique with a percutaneous US-guided peel-away technique, the latter offers advantages such as shorter operating time and lower perioperative complication rates.

Ventriculoatrial Shunts: Review of Technical Aspects and Complications

Diversion of cerebrospinal fluid is required in many neurosurgical conditions. When a standard ventriculoperitoneal shunt and endoscopic third ventriculostomy are not appropriate options, placement of a ventriculoatrial shunt is a safe, relatively familiar second-line shunting procedure. Herein we reviewed the technical aspects of ventriculoatrial shunt placement using an illustrative case. We focused on the different modalities for inserting and confirming the location of the distal catheter tip. We discussed how to overcome typical difficulties and significant concerns, such as cardiac arrhythmias and venous thrombosis. In addition, we reviewed the current literature for the different complications associated with ventriculoatrial shunt placement.

Thrombosis associated with ventriculoatrial shunts

Ventriculoatrial shunts are the most common second-line procedure for cases in which ventriculoperitoneal shunts are unsuitable. Shunting-associated thrombosis is a potentially life-threatening complication after ventriculoatrial shunt insertion. The overall prevalence of this complication is still controversial because of substantial differences in the numbers found in studies using clinical data and in those analyzing postmortem findings. The etiology of thrombosis may be multifactorial, including shunt catheter itself, contents of cerebrospinal fluid, shunt infection, and genetic disorder. The clinical presentation can vary widely, ranging from asymptomatic to a life-threatening condition. Timely recognition of thromboembolic lesions is critical for treatment. However, early diagnosis and management is still challenging because of a relatively long asymptomatic latency and lack of clear guideline recommendations. The purpose of this review is to provide an overview of ventriculoatrial shunt thrombosis, especially to focus on its etiopathogenesis, diagnosis, treatment, and prevention.

Should not we be using aspirin in patients with a ventriculoatrial shunt? Borrowing a leaf from other specialities: a case for surrogate evidence

INTRODUCTION

Ventriculoatrial (VA) shunts are life-saving in circumstances where ventriculoperitoneal shunts (VP) have failed. They are at risk for different complications, and more specific of them are cardiopulmonary complications. Currently, there are no standard recommendations concerning screening for risk factors, prophylaxis, or anticoagulation treatment in patients after VA shunt placement. Our study aims to prospectively study the possible role and efficacy of the use of aspirin to increase the survival of shunts in children with VA shunt and avoid secondary morbidity. In this article, the authors describe the interim results of an ongoing prospective study which supports the use of aspirin for VA shunt.

MATERIALS AND METHODS

The study design is prospective. The duration of the study is 2011 onwards and is ongoing. Hospital ethics board clearance and consent from the family were taken before inclusion in the study. All patients who had VA shunt were given a once-a-day low-antiplatelet dose of aspirin 5 mg/kg, from the first postoperative day onwards. Primary endpoints of the study are as follows: (1) major distal end malfunction documented on echocardiography or (2) any cardiac complications associated with the VA shunt catheter.

RESULTS

We have 6 patient since march 2011, who are being followed up. None of the shunts had malfunctioned until the reporting. None of the patients had any cardiac issues reported. The patients are to be followed continually. The present follow-up ranges from 2.5 to 10 years. The patient follow-up is being continued.

CONCLUSIONS

Aspirin is a drug with well-accepted safety profile, and its use and our preliminary observation and outcome of the use of aspirin in VA shunt are promising.

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus

Among the various disorders that manifest with gait disturbance, cognitive impairment, and urinary incontinence in the elderly population, idiopathic normal pressure hydrocephalus (iNPH) is becoming of great importance. The first edition of these guidelines for management of iNPH was published in 2004, and the second edition in 2012, to provide a series of timely, evidence-based recommendations related to iNPH. Since the last edition, clinical awareness of iNPH has risen dramatically, and clinical and basic research efforts on iNPH have increased significantly. This third edition of the guidelines was made to share these ideas with the international community and to promote international research on iNPH. The revision of the guidelines was undertaken by a multidisciplinary expert working group of the Japanese Society of Normal Pressure Hydrocephalus in conjunction with the Japanese Ministry of Health, Labour and Welfare research project. This revision proposes a new classification for NPH. The category of iNPH is clearly distinguished from NPH with congenital/developmental and acquired etiologies. Additionally, the essential role of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) in the imaging diagnosis and decision for further management of iNPH is discussed in this edition. We created an algorithm for diagnosis and decision for shunt management. Diagnosis by biomarkers that distinguish prognosis has been also initiated. Therefore, diagnosis and treatment of iNPH have entered a new phase. We hope that this third edition of the guidelines will help patients, their families, and healthcare professionals involved in treating iNPH.

Minimally invasive procedure for removal of infected ventriculoatrial shunts

BACKGROUND

Ventriculoatrial shunts were one of the most common treatments of hydrocephalus in pediatric and adult patients up to about 40 years ago. Thereafter, due to the widespread recognition of the severe cardiac and renal complications associated with ventriculoatrial shunts, they are almost exclusively implanted when other techniques fail. However, late infection or atrial thrombi of previously implanted shunts require removal of the atrial catheter several decades after implantation. Techniques derived from management of central venous access catheters can avoid cardiothoracic surgery in such instances.

METHODS

We retrospectively investigated all the patients requiring removal of a VA shunt for complications treated in the last 5 years in our institution.

RESULTS

We identified two patients that were implanted 28 and 40 years earlier. Both developed endocarditis with a large atrial thrombus and were successfully treated endovascularly. The successful percutaneous removal was achieved by applying, for the first time in this setting, the endoluminal dilation technique as proposed by Hong. After ventriculoatrial shunt removal and its substitution with an external drainage, both patients where successfully weaned from the need for a shunt and their infection resolved.

CONCLUSION

Patients carrying a ventriculoatrial shunt are now rarely seen and awareness of long-term ventriculoatrial shunt complications is decreasing. However, these complications must be recognized and treated by shunt removal. Endovascular techniques are appropriate even in the presence of overt endocarditis, atrial thrombi, and tight adherence to the endocardial wall. Moreover, weaning from shunt dependence is possible even decades after shunting.

Ventriculoatrial and ventriculopleural shunts as second-line surgical treatment have equivalent revision, infection, and survival rates in paediatric hydrocephalus

PURPOSE

Ventriculoatrial (VA) and ventriculopleural (VPL) shunts are used as alternatives when CSF diversion to the peritoneal compartment with a ventriculoperitoneal (VP) shunt is not possible. The objective of this study is to compare directly the shunt survival and complications for both procedures in this setting in children.

METHODS

A retrospective analysis of 54 consecutive patients who underwent VA (36) or VPL (18) shunt insertion between January 2002 and December 2017 was conducted.

RESULTS

The overall mean follow-up was 4.1 (SD 4.3) years, 2.8 (SD 4.1) for VPL and 4.7 (SD 4.4) for VA shunts, respectively (p = 0.11). Twenty-four (66.7%) patients in the VA group and 9 (50.0%) in the VPL group underwent shunt revision (p = 0.236); mean number of revisions was 2.2 (SD 3.0) and 0.94 (SD 1.4) in the VA and VPL groups (p = 0.079). Median time to failure was 8.5 (IQr 78, range 0-176) months for VA and 5.50 (IQr 36, range 0-60) for VPL shunts (log rank (Mantel-Cox) 0.832). Shunt survival at 3, 6, 12 and 30 months was 60.6, 51.5, 36.4 and 27.3%, respectively, for VA and 56.3, 43.8, 37.5 and 37.5% for VPL shunts (log rank (Mantel-Cox) test value 0.727). The infection rate was 13.8% for VA and 5.6% for VPL shunts (p = 0.358). Four patients with VPL shunts (22.2%) developed pleural effusions. Fourteen deaths (25.9%) were recorded during follow-up, 8 (22.2%) in the VA and 6 (33.3%) in the VPL group (p = 0.380); two of the deaths in the VA group were shunt-related.

CONCLUSION

This study demonstrates that the outcomes of VA and VPL shunts, when used as second-line surgical treatment in paediatric hydrocephalus, were similar, as were the revision, infection and survival rates. The shorter longevity of these shunts compared with the general shunted population may reflect the complex nature of these children.

Case Series of Ventriculoatrial Shunt placement in Hybrid Room: Reassessment of Ventriculoatrial Shunt

Objective

Ventriculoatrial shunt (VAS) remains an alternate option for treatment of hydrocephalus in patients with ventriculoperitoneal shunt (VPS) failure. Unfamiliar anatomy for a neurosurgeon has resulted in the VAS falling out of favor as a treatment option. However, there are unsatisfactory reports on the long-term result of VPS, and VAS has been recently re-evaluated. We are to report the simple way to do the VAS using a peel-away sheath in a hybrid operation room.

Methods

A jugular vein path was drawn by ultrasound, a small incision was made above the clavicle, and a shunt catheter was tunneled into it. The jugular vein was punctured beside the tunneled catheter with a Seldinger needle under ultrasound guidance. A flexible guide wire was introduced into the vein and 6-Fr peel-away sheath was advanced into the vein along the wire. Under fluoroscopic guidance, the catheter was cut to position approximately mid-level in the atrium. After the guide wire was removed, the distal shunt catheter was passed down. After confirming proper position of the distal catheter under the fluoroscope, the catheter-guiding sheath was pulled out as a peeling-away manner. We performed this surgical procedures in 5 cases.

Results

All the procedures of the VAS using a peel-away sheath were performed in a hybrid operation room Of 5 patients, 3 patients had the distal catheter failures in the peritoneal cavity and 2 patients had shunt A distal catheter was successfully indwelling in all the cases without any difficulties. After the surgery, neither shunt infection nor thromboembolic event happened.

Conclusion

VAS using fluoroscopy and a peel-away sheath is a good alternative option for hydrocephalus patients with shunt failure related to peritoneal cavity complications.

A new dynamic model for in vitro evaluation of intravascular devices

INTRODUCTION:

A dynamic model to evaluate thrombus formation on intravascular catheters in vitro is presented. The model enables fluid infusion, variation in the catheter orientation, and variable flow conditions. It was applied on a catheter used to shunt cerebrospinal fluid to a vein, a dural venous sinus, for the treatment of hydrocephalus.

METHODS:

Fresh human blood-filled circuits were circulated in a non-occlusive roller pump. A catheter infused either with cerebrospinal fluid, Ringer's lactate, or no fluid (control) was inserted through each circuit's wall. Sixteen circuits (six cerebrospinal fluid, six Ringer's lactate, four control) ran for 60 min. Qualitative assessment was performed by measuring viscoelastic properties of blood at the start and end of the experiment; quantitative evaluation of clot formation by scanning electron microscope.

RESULTS:

Average blood velocity was 79 mm/s, with a pressure wave between 5 and 15 mm Hg. At the experiment's end, the infused fluid represented 5.88% of the blood/infusion volume in the circuit. The control circuits showed no statistical difference between the start and end for viscoelastic testing, whereas both Ringer's lactate and cerebrospinal fluid enhanced coagulation, most pronounced for the latter. Most thrombus material was observed on catheters in the cerebrospinal fluid group. Clot formation was less pronounced on the surface of the catheter facing the blood flow.

DISCUSSION:

A dynamic model for intravascular catheter testing mimics better clinical conditions when evaluating blood-material interaction. Catheter position, blood flow around the catheter, and infusion fluid all have a potential impact on the hemocompatibility of a given catheter.

Pleural effusion in a child with a ventriculoperitoneal shunt and congenital heart disease

We present the unique case of an 8 month old infant who required extracorporeal membrane oxygenation (ECMO) after neonatal repair of tetralogy of Fallot. While on ECMO, he developed grade 3 intraventricular hemorrhage resulting in hydrocephalus requiring ventriculoperitoneal (VP) shunt placement at 5 months of life. He presented to cardiology clinic with a 2-month history of poor weight gain, tachypnea, and grunting and was found to have a large right sided pleural effusion. This was proven to be cerebrospinal fluid (CSF) accumulation secondary to poor peritoneal absorption with subsequent extravasation of CSF into the thoracic cavity via a diaphragmatic defect. After diaphragm repair, worsening ascites from peritoneal malabsorption led to shunt externalization and ultimate conversion to a ventriculoatrial (VA) shunt. This is the second reported case of VA shunt placement in a child with congenital heart disease and highlights the need to consider CSF extravasation as the cause of pleural effusions in children with VP shunts.

Ultrasound guided placement of the distal catheter in paediatric ventriculoatrial shunts-an appraisal of efficacy and complications

PURPOSE

Ventriculoatrial (VA) shunts are commonly used as a second-line treatment of hydrocephalus when the peritoneum is an unsuitable site for the distal catheter. Many centres now utilise ultrasound and interventional radiology techniques to aid placement of the distal catheter. The purpose of this study was to conduct a contemporary audit of VA shunting in children using interventional radiology techniques for placement of the distal catheter.

METHODS

A retrospective analysis of all patients who had VA shunts inserted between June 2000 and June 2010 was conducted using a prospectively updated surgical database and case notes review.

RESULTS

Ninety-four VA shunts were inserted in 38 patients. Thirty-seven patients had been treated initially with ventriculoperitoneal (VP) shunts. Twenty-two patients required at least 1 shunt revision (58 %). The 6-month, 1- and 2-year shunt survival rates were 53, 43 and 27 %, respectively. Blockage was the commonest reason for shunt failure (68 %). The site of failure was proximal (ventricular catheter +/- valve) in 32 % and distal (atrial catheter) in 21 % of cases. The overall infection rate was 6 % per procedure and 11 % per patient. There were 7 deaths, of which 3 were shunt related.

CONCLUSIONS

VA shunting provides a viable second-line option for shunt placement in complex hydrocephalus. The causes of shunt failure (blockage, infection and equipment failure) are similar to VP shunting though shunt survival rates are inferior to VP shunts. Ultrasound guided VA shunt placement provides a relatively safe, second-line alternative to the placement of a ventriculoperitoneal shunt when this route is unsuitable.

Robert H. Pudenz (1911-1998) and Ventriculoatrial Shunt: Historical Perspective

Robert H. Pudenz was a renowned neurosurgeon in North America in the 20th century, famous for his contributions in the evolution of the shunt valve and ventriculoatrial shunt surgery. With his innovative idea and help from Heyer, in 1955, he demonstrated that a venous catheter worked best when in the right atrium and that the slit valve should be located at the most distal portion of the shunt system to prevent retrograde filling and thrombosis. He also contributed to various experimental studies on the brain, especially the electrical response of different neural structures. This historical vignette focuses on the work of Robert Pudenz and the evolution of the ventriculoatrial shunt.

Imaging evaluation of CSF shunts

OBJECTIVE

The objective of this article is to describe an approach to imaging CSF shunts. Topics reviewed include the components and imaging appearances of the most common types of shunts and the utility of different imaging modalities for the evaluation of shunt failure. Complications discussed include mechanical failure, infection, ventricular loculation, overdrainage, and unique complications related to each shunt type.

CONCLUSION

This article reviews the imaging features of common CSF shunts and related complications with which radiologists should be familiar.

Pulmonary hypertension after ventriculoatrial shunt implantation

Object

Ventriculoatrial (VA) shunts inserted for the treatment of hydrocephalus are known to be a risk factor for pulmonary hypertension. The aim of this study was to evaluate the incidence of pulmonary hypertension among adult patients with VA shunts.

Methods

All patients who had received a VA shunt at one of two institutions between 1985 and 2000 were invited for a cardiopulmonary evaluation. The investigation included a thorough history taking, clinical examination, echocardiography, and pulmonary function testing including diffusing capacity of the lung for carbon monoxide (DLCO). Pulmonary hypertension was defined as systolic pulmonary artery pressure > 35 mm Hg at rest.

Results

The study group consisted of 86 patients, of whom 38 (44%) could be examined. The patients' mean age was 47.1 ± 18.4 years; the median interval between shunt insertion and cardiopulmonary evaluation was 15 years (range 5–20 years). Of the 38 patients, 20 (53%) had Doppler velocity profiles of tricuspid regurgitation that were adequate for the estimation of pulmonary artery systolic pressure. Doppler-defined pulmonary hypertension was observed in 3 patients (8%), 2 of whom underwent right heart catheterization. Chronic thromboembolic pulmonary hypertension was confirmed in both patients, and medical therapy, including anticoagulation, was started. The VA shunt was removed in both cases and replaced with a different type of device. Pulmonary function tests revealed a restrictive pattern in 15% and typical obstructive findings in 9% of patients. In 30% of patients the DLCO was less than 80% of predicted, and blood gas analysis showed hypoxemia in 6% of patients. No significant differences in pulmonary function tests were noted between the patients with and without echocardiographic evidence of pulmonary hypertension. However, patients with pulmonary hypertension had significantly lower DLCO values.

Conclusions

The authors detected pulmonary hypertension by using Doppler echocardiography in a significant proportion of patients with VA shunts. It is therefore recommended that practitioners perform regular echocardiography and pulmonary function tests, including single-breath DLCO in these patients to screen for pulmonary hypertension to prevent hazardous late cardiopulmonary complications.

Huge thrombosis as a consequence of VA-shunts

OBJECTIVE

Thrombosis is a rare but serious consequence of VA-shunts. We present two cases of near fatal thrombosis and its successful (but in case 2, atypical) management.

RESULTS

Case 1: A 38-year-old woman with VA-shunt suffered from rapidly progressing heart failure and later from progressing underdrainage signs nine years after shunting due to a thrombus on the atrial shunt catheter that occluded >80% of the right atrium. Cardio-surgical removal of thrombus and VA-shunt catheter and VP-shunting normalized neurological and cardiological state. Case 2: A 40-year-old woman received a VA-shunt 5 years before she suddenly suffered dyspnea and venous congestion. Secondarily, underdrainage occurred. The underlying huge thrombosis of the superior caval vein could not be excised because the necessary thoracotomy would have interrupted vital venous bypasses along the thoracic wall. Anticoagulants (heparin, cumarin) and ETV relieved all neurological and cardiological symptoms.

CONCLUSION

Sudden or unexpected symptoms of cardiac failure in the presence of a VA-shunt must be recognized as serious. Interestingly, despite distal shunt occlusion, underdrainage symptoms might be initially mild.

Thrombosis associated with ventriculoatrial shunts

OBJECT

In this single-center study, the authors examined the clinical characteristics, risk factors, treatment strategies, and outcomes in patients with thrombosis associated with ventriculoatrial (VA) shunts.

METHODS

Inpatient and outpatient charts of patients who underwent treatment and follow-up in the Hematology-Oncology Division at the authors' institution and in whom thrombosis developed secondary to a VA shunt placement were reviewed. A complete thrombophilia work-up was performed in each patient, and these records were also reviewed. Treatment including medical and surgical management was noted and outcome data were recorded.

RESULTS

Resolution of thrombosis was seen after anticoagulation therapy in all patients; this may be an alternative to surgical therapy.

CONCLUSIONS

Patients with VA shunts represent a unique group at risk for thrombosis. The duration of anticoagulation therapy must be individualized. However, larger studies are needed to evaluate the efficacy of screening for asymptomatic thrombosis and to investigate the role of prophylactic anticoagulation.

Pulmonary hypertension: a rare but serious complication of ventriculoatrial shunts

A 34-year-old woman presented with a 6-month history of progressive dyspnoea. Past history included cerebral palsy and epilepsy. At the age of 14 years she had a ventriculoatrial (VA) shunt for hydrocephalus secondary to congenital aqueduct stenosis. There was no past history of deep vein thrombosis, liver disease, appetite suppressant use, intravenous drug abuse or other systemic disease.

On examination she was unwell with central cyanosis, tachypnoea (respiratory rate 36 breaths per minute), sinus tachycardia (heart rate 120 beats per minute), and blood pressure 100/60 mmHg. There was ankle oedema, raised jugular venous pressure, accentuated pulmonary second sound and a right ventricular gallop.

Chest X-ray showed cardiomegaly with prominent pulmonary arteries (Figure 1). Electrocardiogram demonstrated right axis deviation, dominant R wave in V1 and ST depression across the precordial leads (Figure 2). On room air her arterial partial pressures of oxygen and carbon dioxide were 7.1 KPa and 3.2 KPa respectively. Transthoracic echocardiography showed dilated right ventricle and right atrium with severe tricuspid regurgitation and moderate pulmonary regurgitation. Estimated pulmonary artery pressure was 100 mmHg. There was no evidence of intracardiac thrombus and left ventricular systolic function normal. A ventilation perfusion scan showed multiple sub-segmental perfusion defects. Cardiac catheterization confirmed severe pulmonary hypertension (pulmonary vascular resistance 1048 dynes/sec/cm2) with normal left heart pressures and no intracardiac shunt. Calculated cardiac index was low (1.5 litre/min/kg) with high right atrial pressure (20 mmHg) and low mixed venous oxygen saturation (50%). Pulmonary angiography and chest computed tomogram with contrast showed thrombus in the main pulmonary trunk extending into the proximal right and left pulmonary arteries. Duplex ultrasonography of both legs suggested no evidence of deep vein thrombosis. A thrombophilia, vasculitis and infection screen was negative.

The patient was commenced on nasal continuous positive airways pressure, high flow oxygen, intravenous heparin and intravenous colloid with haemodynamic stability maintained for the first 4 days. After this she became more hypoxic and hypotensive so fluids were stopped and a frusemide, dopamine and prostacyclin infusion commenced to reduce right ventricular distension with some improvement. Because of her deteriorating haemodynamic state, pulmonary thromboendarterectomy was performed with removal of extensive thrombus from the proximal pulmonary tree. The patient died in the immediate postoperative period.

Postmortem showed a distended and hypertrophied right heart with extensive chronic thromboembolic changes in the distal pulmonary tree. The tip of the VA catheter in the right atrium had no signs of infection and at this time was free of thrombus. The coroner concluded cause of death was pulmonary hypertension secondary to longstanding thromboembolic disease.

Pathophysiology, Diagnosis, and Management of Pulmonary Hypertension in Infants and Children

Pulmonary hypertension (PH) may occur as a primary process or as a complication of several diseases. In the pediatric population, PH secondary to congenital heart disease, chronic hypoxemia, or acute respiratory failure is more common than primary PH. Regardless of etiology, PH may lead to significant morbidity or mortality as a consequence of right-to-left shunting across cardiovascular channels or right heart failure. In this review, PH is defined in terms of the determinants of pulmonary blood flow: pulmonary artery pressure, downstream pressure, and pulmonary vascular resistance. Research addressing both normal developmental changes in pulmonary vascular resistance and abnormal pulmonary vascular reactivity is then reviewed, followed by a discussion of the etiologies of PH in children. Some of the more common clinical presentations of PH are presented focussing on the differences seen between patients with and without intracardiac communications. Assessment of the severity of PH using both noninvasive (electrocardiogram, echocardiogram, magnetic resonance imaging) and invasive (cardiac catheterization, lung biopsy) techniques is then discussed. Treatment of PH is presented, focussing on restoration of adequate pulmonary blood flow through use of both conventional and newer vasodilator therapies. The review concludes by noting the limits to our understanding of the pathogenesis and therapy of PH.

Valved conduit bypass for extensively calcified tricuspid valve stenosis

A case of calcified tricuspid valve stenosis resulting from a complication of ventriculoatrial shunt implantation is presented. Tricuspid valve repair or replacement was not possible because of the prohibitive risk of damaging the right atrioventricular junction and conductive pathways. This rare lesion was treated successfully by insertion of an external right atrial-right ventricular valved conduit. The role of echocardiography in the detection of such a lesion is emphasized and the etiologic and therapeutic aspects are discussed.