Open heart surgery involves cutting through the breastbone to reach the heart, connecting the patient to a machine that temporarily does the work of the heart and lungs, and then repairing or replacing whatever is damaged. The entire process typically takes three to six hours, and survival rates for most procedures now exceed 95%. Here’s what happens at each stage, from the moment the patient is wheeled into the operating room to the first days of recovery.
Preparing the Patient
Before anyone picks up a scalpel, the anesthesia team places the patient under general anesthesia using a combination of a pain-blocking drug, a sedative, and a muscle relaxant. A thin tube called a catheter is threaded into an artery in the wrist to continuously monitor blood pressure. Additional monitoring tracks heart rhythm across five channels, oxygen levels in the blood and brain, body temperature, and brain wave activity to ensure the patient stays at the right depth of sedation throughout the procedure.
A breathing tube is placed into the windpipe and connected to a ventilator, which will control the patient’s breathing for the duration of the surgery and into the early hours of recovery. An ultrasound probe is also guided down the throat to give surgeons a live image of the heart from the inside of the esophagus. This lets them check the heart’s structures before, during, and after the repair.
Opening the Chest
The surgeon makes a vertical incision down the center of the chest, typically 8 to 10 inches long. Beneath the skin, the breastbone (sternum) is cut lengthwise using an oscillating saw, a tool that vibrates rather than spins, which gives more control and reduces damage to surrounding tissue. A metal retractor is then cranked open to spread the two halves of the breastbone apart, creating a window to the heart.
The protective sac around the heart, called the pericardium, is opened with a vertical cut. Small stitches are placed along its edges and pulled outward to hold it open, giving the surgeon a clear, stable view of the heart and major blood vessels.
Connecting the Heart-Lung Machine
This is the step that defines open heart surgery. Plastic tubes are inserted into the large veins entering the heart and into the aorta, the main artery leaving the heart. These tubes reroute the patient’s blood to a machine sitting beside the operating table. The machine, run by a specialist called a perfusionist, does three things: it adds oxygen to the blood, removes carbon dioxide, and pumps the refreshed blood back into the body through the aorta. It also controls blood temperature and electrolyte balance.
Once the machine takes over circulation, the surgeon places a clamp across the aorta to isolate the heart from the rest of the bloodstream. A potassium-rich solution is then flushed into the heart’s own blood vessels. The high potassium concentration causes the heart muscle to relax and stop beating in a controlled way, dramatically reducing its need for oxygen. This solution can be delivered cold (around 4°C) to further slow the heart’s metabolism, or warm (around 35°C) when mixed with the patient’s own blood. Either way, the result is a still, protected heart that the surgeon can work on without it moving or sustaining damage from oxygen deprivation.
What the Surgeon Actually Repairs
The specific repair depends on the condition. The two most common open heart procedures are coronary artery bypass grafting (CABG) and valve replacement or repair.
Coronary Artery Bypass
In a bypass, the surgeon takes a healthy blood vessel from another part of the body, often a vein from the leg or an artery from inside the chest wall, and uses it to create a detour around a blocked coronary artery. One end of the graft is sewn to the aorta and the other end is sewn to the coronary artery below the blockage, restoring blood flow to the starved section of heart muscle.
The sewing itself is extraordinarily precise. Surgeons use thread thinner than a human hair (polypropylene sutures as fine as 7-0 or 8-0 gauge) and continuous stitching techniques to connect the graft to arteries that can be smaller than 1.2 millimeters across. Each connection point is anchored with three small stitches at the top and bottom before the rest of the seam is completed, ensuring the tiny opening stays open and blood flows freely. Patients who need multiple bypasses may have three, four, or even five of these grafts placed in a single operation.
Valve Replacement
For a damaged valve, the surgeon opens the relevant chamber or blood vessel, removes the diseased valve, and sews in either a mechanical replacement (made of carbon and metal) or a biological one (made from animal tissue). The aortic valve, for example, is accessed by cutting across the aorta just above the valve, removing the old valve leaflets, and stitching the new valve into place around the ring where the old one sat.
Restarting the Heart
Once the repair is complete, the surgeon removes the aortic clamp, allowing warm blood to flow back into the heart’s own arteries. As the heart warms and the potassium solution washes out, the muscle often begins beating on its own. If it doesn’t restart spontaneously or falls into an irregular rhythm, small internal paddles deliver a mild electric shock directly to the heart to restore a normal beat.
The surgical team watches the heart closely for several minutes, checking that it’s pumping effectively and that the repair looks good on the ultrasound probe still positioned in the esophagus. Once they’re satisfied, the heart-lung machine is gradually dialed down and the patient’s heart and lungs resume full responsibility for circulation. The bypass tubes are removed.
Closing the Chest
Rejoining the breastbone is a critical step. The standard method uses stainless steel wires threaded around or through the sternum and twisted tight to hold the two halves together. Most closures use six or more wires placed across the bone in a simple loop or figure-of-eight pattern. For patients at higher risk of the bone separating (such as those with osteoporosis or diabetes), surgeons may reinforce the closure with titanium plates secured by small screws, or use a modified technique that adds wires running lengthwise along each side of the sternum for extra stability.
Drainage tubes are placed in the chest to collect any fluid that accumulates in the first day or two. The layers of tissue, muscle, and skin above the sternum are sutured closed, and the incision is bandaged.
The First Days of Recovery
The patient goes directly from the operating room to the intensive care unit, still on the ventilator and sedated. As sedation wears off, the breathing tube is removed, usually within 6 to 24 hours after surgery. Most patients are breathing on their own by the first day. Even while still on the ventilator, the care team will sit the patient up in bed to start preventing complications from prolonged immobility.
Within 12 to 48 hours after surgery, patients who are stable are transferred out of the ICU to a step-down unit. Standing and walking short distances begin as soon as the patient feels strong enough, which for many people is within the first two days. The chest drainage tubes come out once fluid output drops to a low level, and the steel wires holding the breastbone together are permanent, though they’re rarely felt once healing is complete. Full recovery of the breastbone takes about six to eight weeks, during which patients are told to avoid lifting heavy objects or pushing and pulling with their arms.
Minimally Invasive Alternatives
Not everyone needs a full sternotomy. Some heart surgeries can now be performed through smaller incisions of 6 to 10 centimeters, cutting only a portion of the breastbone or working between the ribs without splitting the sternum at all. A right mini-thoracotomy, for instance, uses a 6 to 7 centimeter incision along the side of the chest to access the heart for valve procedures.
These approaches result in significantly less postoperative pain compared to a full sternotomy, and because less bone is cut, patients can change positions, cough, and move around more easily in the early recovery period. Lung function is also better preserved. However, ICU stay and time on the ventilator are similar between the two approaches, and not every patient or condition is suitable for a smaller incision. The surgeon’s experience with these techniques also plays a role in which approach is offered.
How Safe Is It?
Open heart surgery is one of the most well-studied procedures in medicine. Overall survival rates now exceed 90% even for emergency cases. For a first-time coronary bypass in otherwise stable patients, 30-day survival is around 98 to 99%. Five-year survival after a first-time bypass is approximately 93%. Patients undergoing repeat bypass surgery or those over 80 have somewhat lower but still favorable odds, with 30-day survival around 94% in octogenarians. The risks are real but have steadily declined over decades of refinement in surgical technique, heart-lung machine technology, and post-operative care.