Heart surgery works by temporarily stopping or rerouting blood flow so a surgeon can repair or replace damaged structures inside the heart. In most open-heart procedures, a machine takes over the job of your heart and lungs while the surgeon operates on a still, bloodless field. The specific steps depend on whether you’re having a bypass, a valve replacement, or another repair, but the core process follows a similar sequence: preparation, rerouting your blood, the repair itself, and closing up.
How Blood Is Rerouted During Surgery
The centerpiece of most heart surgeries is a process called cardiopulmonary bypass. Tubes are inserted into your blood vessels so that instead of flowing through your heart and lungs, your blood drains into a machine outside your body. Inside that machine, an oxygenator adds oxygen to your blood and strips out carbon dioxide, doing exactly what your lungs would normally do. The machine then pumps the refreshed blood back into your body through a tube connected to your aorta, the large artery that distributes blood to the rest of you.
With the machine handling circulation, your heart can be temporarily stopped using a cold solution. This gives the surgeon a motionless, mostly bloodless workspace. Some newer procedures skip this step entirely, operating on a beating heart, but the bypass machine remains the standard approach for most major cardiac operations.
Getting to the Heart: Incision Types
The traditional approach is a midline incision through the breastbone. For bypass operations, this incision runs about 12 to 15 centimeters. Valve procedures use a somewhat shorter cut: 8 to 10 centimeters for aortic valve surgery, 10 to 12 centimeters for mitral valve surgery. The breastbone is split with a saw and held open with a retractor, giving the surgeon direct access to the heart.
Robotic and minimally invasive techniques use much smaller incisions, often just a few small ports between the ribs. The surgeon controls robotic arms from a console while watching a magnified 3D image of the heart. These approaches aren’t suitable for every patient or every type of repair, but when they can be used, they cut hospital stays roughly in half. Robotic surgery patients typically go home in 2 to 4 days, compared to a week or more after traditional open-heart surgery.
How Bypass Surgery Repairs Blocked Arteries
Coronary artery bypass grafting (CABG) is the most common type of heart surgery. When one or more arteries supplying blood to the heart muscle are severely narrowed or blocked, the surgeon creates a detour around each blockage using a healthy blood vessel taken from somewhere else in your body.
The most commonly used graft comes from an artery inside the chest wall, called the internal mammary artery. This vessel is prized because it tends to stay open longer than other grafts. When additional grafts are needed, surgeons often harvest a vein from the lower leg called the saphenous vein. One end of the graft is sewn above the blockage and the other end below it, creating a new path for blood to reach the starved heart muscle. Patients with multiple blockages may receive two, three, or even five grafts in a single operation, which is where terms like “triple bypass” or “quintuple bypass” come from.
The 30-day mortality rate for isolated bypass surgery has dropped to around 2 to 3 percent in recent years, making it one of the most well-studied and refined operations in medicine.
How Valve Replacement Works
Your heart has four valves that open and close with each heartbeat to keep blood moving in one direction. When a valve becomes too narrow to open fully or too loose to close properly, it can be repaired or replaced surgically.
In traditional open surgical valve replacement, the surgeon opens the chest, places you on the bypass machine, removes the damaged valve, and sews in a new one. Replacement valves are either mechanical (made from durable materials and designed to last decades) or biological (made from animal tissue, which feels more natural to the body but wears out over time).
For aortic valve disease specifically, there’s now a less invasive option. Instead of opening the chest, a new valve is compressed onto a catheter, threaded through a blood vessel in the leg, and guided up to the heart. Once in position, the valve expands and pushes the old valve aside. U.S. guidelines now consider this catheter-based approach an equal alternative to open surgery for patients aged 65 to 80, and the preferred option for patients over 80.
What Happens Before Surgery
In the weeks before your operation, your medical team maps out your heart in detail. This typically includes an electrocardiogram to check your heart’s electrical activity, an echocardiogram (an ultrasound of the heart) to see how well it’s pumping and how the valves are functioning, and blood tests to assess your overall health. Many patients also undergo cardiac catheterization, where a thin tube is threaded into the heart’s arteries and dye is injected so blockages show up on X-ray. Additional imaging like CT scans, MRIs, or stress tests may be ordered depending on the procedure.
You’ll be asked to stop certain medications, particularly blood thinners, several days before surgery. Smoking cessation is strongly encouraged because it significantly affects how well your lungs recover afterward.
Anesthesia and the Operating Room
Heart surgery is performed under general anesthesia. An anesthesiologist administers a combination of drugs that put you into a deep, controlled unconsciousness while also relaxing your muscles completely so the surgeon can work without any movement. A breathing tube is placed in your airway and connected to a ventilator, which breathes for you throughout the procedure.
The anesthesia team monitors your brain activity, blood pressure, oxygen levels, and heart rhythm continuously. They adjust medications in real time to keep you stable, especially during the critical moments when your heart is stopped and the bypass machine takes over, and again when your heart is restarted at the end of the operation.
What Recovery Looks Like
After surgery, you wake up in the intensive care unit with the breathing tube still in place. Once you’re conscious and breathing well on your own, usually within hours, the tube is removed. You’ll have chest tubes draining fluid from around your heart, IV lines delivering medications, and monitors tracking your heart rhythm and blood pressure around the clock. Most patients spend 1 to 3 days in the ICU before moving to a regular hospital room, where these tubes and monitors are gradually removed over the following days.
The breastbone takes the longest to heal. For 8 to 12 weeks after surgery, you’ll follow sternal precautions, which means avoiding lifting anything heavier than about 2 pounds (roughly 1 kilogram) and not pushing or pulling with your upper body. This protects the bone while it knits back together. You won’t be able to drive during this period, and most people take 6 to 12 weeks off work depending on how physical their job is.
Cardiac rehabilitation, a supervised exercise and education program, typically starts a few weeks after discharge. It gradually rebuilds your stamina and confidence. Most people report feeling significantly better than they did before surgery within 3 to 6 months, though full recovery of energy and strength can take longer.