The death of 38-year-old Prateek Yadav, son of Samajwadi Party (SP) founder Mulayam Singh Yadav, due to pulmonary embolism and heart complications has once again spotlighted a medical emergency that is often sudden, difficult to detect and, if missed, can be fatal.Unlike a heart attack, which occurs when blood flow to the heart muscle is blocked, a pulmonary embolism happens when a blood clot blocks one of the arteries supplying blood to the lungs. “This is like a pileup in one of the body’s most critical highways. And because the lungs are central to oxygenating blood, even a single large clot there can quickly trigger collapse of all body systems,” says Dr Nishith Chandra, principal director, cardiology, Fortis Escorts Heart Institute Research Centre, New Delhi. Excerpts:What is pulmonary embolism?To understand pulmonary embolism or lung clots, it helps to understand how quickly the body’s circulation works. The heart beats about 60 to 70 times every minute. In that time, roughly the body’s entire blood volume — about five to six litres — completes one full pulmonary circulation cycle. Oxygen-scarce blood returns from the body to the right side of the heart. The right ventricle pumps it into the pulmonary arteries, which carry it to the lungs, where it releases carbon dioxide and picks up oxygen. The oxygen-rich blood then returns to the left side of the heart, which pumps it back to the rest of the body. This oxygenation loop is completed in seconds.When a clot blocks a pulmonary artery, that loop is disrupted. Blood cannot reach parts of the lung for oxygenation, oxygen levels fall and the heart is suddenly forced to pump against intense resistance. If the clot is large enough, the right side of the heart can fail within minutes.Where the clot usually comes fromMost clots usually begin with a deep vein thrombosis (DVT) when a clot forms in the deep veins of the legs, pelvis or sometimes the arms. Veins carry deoxygenated blood back to the heart. Part of that clot can break off, travel through the venous system, pass through the right side of the heart and lodge in the pulmonary arteries.What causes such clots?Several conditions increase this risk. Prolonged bed rest after illness, surgeries or cancer therapies, prolonged sedentary behaviour like sitting in long haul flights, even dehydration. In all these situations, blood flow slows down, making clot formation more likely. DVT happens in the leg because blood naturally moves more slowly there, and if movement drops or clotting risk rises, those veins become the easiest place for a clot to form.Can aggressive gym practices contribute to DVT?We are told that Prateek was fitness conscious and worked out. But being physically active does not automatically protect against blood clots, especially when other risk factors are present. One common reason is dehydration. Heavy workouts, excessive sweating, sauna use, aggressive cutting cycles or inadequate fluid intake can reduce plasma volume and make blood thicker, which increases the tendency to clot.Story continues below this adAnother concern is the misuse of muscle-building injections, anabolic steroids, testosterone boosters or other performance-enhancing substances, particularly when taken without medical supervision. These can increase red blood cell production, thicken the blood, alter clotting mechanisms and sometimes damage blood vessels, making clot formation more likely.Some intense gym users also combine these with high-protein, dehydration-prone diets, stimulant-heavy pre-workout supplements and inadequate recovery. We regularly see such cases. That said, regular exercise, done safely, reduces clot risk.What are symptoms?A pulmonary embolism can be very abrupt. The person may experience sudden breathlessness, chest pain, rapid heartbeat, sweating, dizziness, bluish lips and collapse. In some massive embolisms, death can occur within minutes.Smaller clots may produce warning signs for days or even a week beforehand, such as unexplained shortness of breath, calf pain, swelling, unusual fatigue or mild chest discomfort. This is why early symptoms are often missed or mistaken for gym soreness, acidity, anxiety or exhaustion.Story continues below this adA dangerous feature of clotting is that one clot attracts more clots and there is a huge formation.Can it be treated?If detected early, pulmonary embolism is often highly treatable. Treatment depends on severity. For smaller clots, doctors use blood thinners to prevent further clot growth and allow the body to gradually dissolve the clot. For severe or life-threatening embolisms, clot-dissolving medicines may be given urgently.In advanced centres, catheter-based devices can physically remove the clot. These include systems such as the Penumbra, which sucks the clot out, AngioJet, which breaks and removes the blockage using high-pressure saline jets. These interventions can rapidly restore circulation. Time is crucial as late presentation remains the biggest reason for mortality.For younger fitness-focused adults, unexplained breathlessness after workouts deserves attention, especially if accompanied by recent injections, dehydration or prolonged immobility. The tragedy of cases like Prateek Yadav’s lies in how deceptive pulmonary embolism can be and that visible fitness is not the same as internal health.