The ominous clot

Venous thromboembolism, which consists of the interrelated diseases of pulmonary embolism and deep-vein thrombosis, is among the top five most common vascular diseases in most countries affecting approximately 5% of the population during their lifetimes, writes Dr Praveen Kumar Kaudlay.

Venous Thromboembolism (VTE), encompassing Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), is a significant preventable cause of morbidity and
mortality worldwide. However, it is often underdiagnosed and underestimated. DVT entails clot formation in the legs, while PE occurs when these clots migrate to the lungs’ blood vessels. VTE ranks as the third most common cardiovascular disorder, affecting approximately 5% of the population during their lifetimes and impacting nearly 10 million individuals annually.

The global incidence of PE is around 1-2 cases per 1,000 people, rising exponentially with age for both genders. In India, definitive data on incidence is lacking. Prof Roopen Arya, director of King’s Thrombosis Centre at King’s Hospital, London and director of the National VTE Exemplar Centres
Network in England, notes that hospital-acquired VTE in India may match that of the West, potentially being under-detected and under-reported. Virchow’s triad, coined in 1856 CE, identifies the key factors in clot formation: venous blood pooling, vessel wall injury, and increased clotting tendency. These factors work together to promote clot formation, exacerbated by the interplay between clotting and inflammation. Conditions such as surgery, trauma, prolonged immobilisation, pregnancy, heart failure, cancer, obesity, varicose veins, and previous leg clots increase
the risk of clot formation. Active cancer is the most common persistent risk factor. However, it’s essential to note that many clotting episodes may occur without identifiable risks.

The scoring system

DVT presents symptoms like leg swelling, warmth, or tenderness. The diagnosis often involves using the Well’s score, a scoring system to assess the likelihood of a clot. Additionally, the D-dimer blood test is commonly employed, measuring a clotting cascade degradation product. However, it’s crucial to note that elevated D-dimer levels may signal clotting but can also be raised in various inflammatory conditions, cancer, pregnancy, post-surgical operations, and liver disorders. Thus, interpretation should account
for the broader clinical context.

However, when coupled with the Well’s score and ultrasound scan, the D-dimer test becomes a valuable tool for ruling out the possibility of clot formation in
low-risk cases. Moreover, testing for pulmonary embolism should be contemplated in any patient with a respiratory condition that fails to respond to treatment. Patients with a strong suspicion of pulmonary embolism should be assessed with a CT Pulmonary Angiogram (CTPA) within 24 hours of presentation. However, factors such as cost and radiation exposure warrant the use of established diagnostic strategies to prioritise patients for scanning. When a CT scan is not viable, a Ventilation-Perfusion scan serves as an alternative diagnostic option. In North America, pulmonary embolism is diagnosed in only one out of every 20 patients tested upon presentation to the emergency department. Intriguingly, the prevalence in Europe is four times higher than in America. In India, the detection rate varies, with tertiary centres exhibiting higher rates due to established protocols and heightened awareness. However, this efficiency is not consistently observed in smaller centres, as noted by Dr Ravindra Mehta, head of Integrated Pulmonary Services at a leading chain of hospitals in Bengaluru.

Who needs prophylaxis 

Fifty per cent of clot events are associated with transient risk factors like recent surgery, hospital stays, and prolonged immobilisation. Therefore, all admitted patients must undergo evaluation for clot formation risks and receive suitable prophylaxis. This could include mechanical protection with elastic stockings or pumps, as well as the administration of heparin drugs to mitigate clotting risk. Dr Satish Sathyanarayana, a Bengaluru-based senior consultant and neuro & spinal surgeon, emphasises the significance of diligent prophylaxis, particularly using mechanical pumps like Flowtron Pumps or Low Molecular Weight Heparins (LMWH), in high-risk individuals undergoing spine or brain surgeries. Similarly, post-operative orthopaedic procedures such as hip replacement necessitate ongoing prophylaxis. Dr Mehta has observed enhanced adherence to prophylaxis in orthopaedic operations and intensive care, resulting in fewer instances of VTE events overall.

Approach to treatment

Initial treatment for DVT depends on the clot’s location, with consideration for the risk of PE. Massive PE cases with acute low blood pressure or cardiac arrest may require clot-bursting drugs, surgical removal, or catheter-assisted techniques. DVT is typically managed with Warfarin, DOACs (newer anticoagulants), or LMWH for blood thinning over 3-6 months. Similarly, PE treatment extends for 3-6 months, with the potential for long-term management if no underlying cause is identified. Recovery from DVT and PE can pose challenges, including chronically swollen legs, decreased exercise capacity, and bleeding risks from anticoagulation treatment.

(The author is a consultant haemato-oncologist with a special interest in stem cell transplantation at Royal Wolverhampton NHS Trust, UK. He can be reached at [e-mail])