Overview of Cardiac Risk Assessment
Many individuals who will undergo major surgeries that do not involve the heart (noncardiac) and vascular surgeries are at risk of major heart-related complications, known as major adverse cardiac events (MACE). Each year in the United States, 27 million people undergo non-heart related surgery and sadly, 50,000 of these people suffer from a heart attack afterwards. It’s important to know that nearly half of all deaths in patients undergoing non-heart related surgeries are linked to heart-related complications. These heart-related complications happen in about 1 to 5 people out of a 100 who undergo vascular surgery.
To decrease these complications and the associated illness and death, we need to carefully evaluate patients with heart disease before surgery. This involves “risk stratification”, which means figuring out how likely it is that a patient will have problems during their operation.
The American College of Cardiology (ACC) and the American Heart Association (AHA) have worked together to create guidelines for checking heart health before non-heart related surgery. These guidelines are based on scientific evidence and aim to standardize how we assess patients’ heart risk before surgery.
According to the guidelines, recommendations are made based on the patient’s history of heart disease or risk factors for heart disease, how well the patient is functioning, and how urgently the surgery is needed. This tailored heart risk assessment aims to reduce the risk of heart complications during surgery, as it could lead to more tests to diagnose heart problems, treatment with medicine, or even procedures to improve blood flow to the heart.
Anatomy and Physiology of Cardiac Risk Assessment
When preparing for surgery, doctors need to check a patient’s heart health to identify any potential risks. This health check involves a detailed examination and some non-invasive tests to gather information on three important heart performance signs: How well the heart pumps blood (LV dysfunction), if there’s a lack of blood supply to the heart muscle (myocardial ischemia), and if there are issues with the heart valves. These factors are crucial as they can impact the patient’s recovery after the surgery.
This careful examination includes checking vital signs like blood pressure, heart rate, breathing rate, temperature, and oxygen levels. The patient’s height, weight and body mass index (BMI), a measure of body fat, are also assessed.
During the physical examination, the doctor pays close attention to the heart and lungs. They listen to the heart and lungs (auscultation), check the pulse, look at the veins, and feel the abdomen. They also examine the arms and legs for swelling and to ensure the blood vessels are in good condition.
They’re also looking out for certain signs that could indicate problems with the heart’s functioning. These include unusual heart sounds, crackling sounds in the lungs (rales), swollen veins in the neck (jugular venous distention), fluid in the abdominal cavity (ascites), an enlarged liver (hepatomegaly), and swelling in the lower body due to fluid buildup (dependent edema). Similarly, if there is an unusual heart murmur, it could indicate significant issues with the heart valves.
Why do People Need Cardiac Risk Assessment
While heart disease can affect people of all ages, complications related to heart health during surgery are more common in adults undergoing significant non-heart-related surgeries. Guidelines provided by the Canadian Cardiovascular Society recommend that anyone over the age of 45, or those between 18 and 44 with serious heart disease, should get a heart risk assessment before having surgery.
There are several risk factors that could increase the chance of negative heart-related outcomes during or after surgery. These are:
* Poor physical fitness
* Heart disease such as prior heart attack, chest pain from heart disease, and so on
* Heart failure
* Cardiomypathy or heart muscle disease
* Serious heart valve disease like severe blockage of a heart valve or surface irregularities of valves
* Serious irregular heart rhythms (conditions like Mobitz II AV block, 3rd-degree block, irregular heart rhythms that cause symptoms, slow heart rate causing symptoms, newly found fast heart rhythms)
* Chronic kidney disease
* History of stroke or mini-stroke
* Diabetes requiring insulin
* Chronic lung disease
* Obesity
* Anemia or low red blood cell count
After a complete physical exam and evaluation of these risk factors, a stepwise process, as recommended by the American College of Cardiology/American Heart Association, is followed to decide if any additional pre-surgery interventions are needed. This process considers factors like the urgency of the surgery, the presence of any active heart conditions, the risk associated with the surgery, and the patient’s physical fitness.
If the patient has any active heart conditions like a recent heart attack, unstable or severe chest pain, serious heart valve disease, or significant irregular heart rhythms, the surgery might need to be delayed unless it’s a life-saving emergency.
Furthermore, this process also assesses the patient’s physical fitness, which can be measured using something called Metabolic Equivalents (METs). One MET is equal to the energy used by a person at rest. This can be objectively measured through exercise testing, or it can be estimated based on a person’s ability to carry out daily activities.
Finally, patients who have low or undetermined METs and are scheduled for intermediate-risk surgery may need further heart testing. This is determined based on the presence of risk factors like heart disease, heart failure, stroke, diabetes, and kidney disease. However, additional tests would only be conducted if the results could alter the surgery plan.
When a Person Should Avoid Cardiac Risk Assessment
When a patient needs emergency surgery, either within a 6 hours’ window (emergency surgery) or between 6 to 24 hours (urgent surgery), there typically isn’t time to carry out a cardiac checkup before the operation. This is because any delay might be harmful to the patient. Due to the rush and the nature of the surgery, these patients stand a higher chance of experiencing a heart-related event during or after the surgery. It’s important, therefore, to monitor the patients carefully for such events during the surgery and to keep on with any ongoing heart-related treatments.
If a patient has a recent history of heart disease, or has other uncontrolled health conditions, or has recently undergone a medical procedure, certain guidelines have to be followed before they can undergo surgery.
When dealing with patients who have high blood pressure, it’s important to not only know their current blood pressure, but also their usual blood pressure before the surgery. This is usually done by studying their medical history and any existing records on their blood pressure medication and the effectiveness of the medication. The checkup should also look for signs of any organ damage due to the high blood pressure. Whether to continue with the blood pressure medication on the day of the surgery remains a debated topic. Some studies have shown that patients who stop their medication on the surgery day didn’t experience any harmful effects. However, it’s important that they resume their medication quickly after the surgery.
Patients with extremely high blood pressure (systolic blood pressure above 180 mmHg and/or diastolic blood pressure above 110 mmHg) requires special attention. In such cases, a balance has to be struck between delaying the surgery to control the blood pressure, and the risks associated with the delay.
Patients who recently had a heart attack or have unstable chest pains are more prone to serious heart-related events. To lower this risk, it’s suggested to wait a minimum of 4-6 weeks after a heart attack before undergoing surgery. Studies show that the longer the time between the heart attack and the surgery, the lower the risk of death within 30 days after the surgery.
Heart failure is also a vital factor to account for before surgery. Heart failure patients are more likely to experience a major heart-related event after surgery. The risk is even higher if the heart failure is deteriorating or not well-managed. Checkups to assess the severity of heart failure are important in planning for the surgery. If the heart failure is severe, it might be necessary to improve the heart’s condition before the surgery to ensure better results.
Checking for blockages in the heart valves (aortic stenosis) before surgery is equally important. Such blockages, particularly if moderate to severe, can double the rate of death within 30 days of the surgery and can cause a postoperative heart attack three times more often. It’s important therefore to determine how serious they are before the surgery, as well as whether the patient has symptoms of the blockages.
Patients with severe aortic stenosis, which requires an urgent procedure, will need careful monitoring during the surgery. For patients with mitral stenosis, or blockage in the valves that regulate blood flow from the heart’s left atrium to the left ventricle, it’s also important to assess the severity of the blockage and the presence of related symptoms before the surgery.
Equipment used for Cardiac Risk Assessment
Pacemaker
Before a surgery in someone with a pacemaker, it’s crucial to know why they need the pacemaker, how much battery life is left in it, and what its current settings are. This is important because during the surgery, some tools like the electrocautery (a device that uses heat for cutting or sealing tissue) might interfere with how the pacemaker works.[3][9]. There are ways to prevent this from happening. One way is to place the ground plate, which is part of the electrical circuit in the device, in a certain position so the electrical current doesn’t affect the pacemaker. Using short, low-intensity bursts of electricity with the electrocautery can also reduce any interference.[3] If relying heavily on the pacemaker, a magnet can be placed on the skin over it. This magnet makes the pacemaker work in a different mode. It’s important after using the magnet to check the pacemaker is still working as expected.[3]
Automatic Implantable Cardioverter Defibrillator (AICD)
People with an AICD, a device that monitors heart rhythms and can deliver electrical shocks to correct irregular rhythms, need to have their AICD deactivated before going through surgery. This ensures the electrocautery won’t accidentally cause the AICD to deliver a shock.[3] Turning off the AICD is done by placing a magnet over it, which converts it into a simple pacemaker mode.
While the AICD is turned off, it’s essential to constantly monitor the patient’s heart rhythm through an electrocardiogram (a test that measures the heart’s electrical signals). And, it’s always important to have the ability to immediately give the heart an external electrical shock if needed.[9]. And remember, it’s essential to turn the AICD back on after the surgery.
Preparing for Cardiac Risk Assessment
One important part of getting ready for heart surgery is a pre-surgery check-up. This helps doctors understand the patient’s heart health before the operation. A few tests are carried out based on proven guidelines.
The first is an electrocardiogram (ECG). This test checks to see if there is any strain on the heart, any unusual heart rhythms, or other heart problems. According to guidelines, this test is given in some specific cases:
- Patients with heart risk factors who are getting ready for medium or high-risk surgery should have an ECG.
- Patients with heart risk factors who are having a low-risk surgery could consider getting an ECG.
- In some cases, an ECG might be considered for patients with no heart risk factors who are having a medium-risk surgery.
- Patients with no heart risk factors who are getting ready for a low-risk surgery don’t need to get an ECG.
The second test is an echocardiogram. This is an ultrasound picture of the heart. Although it’s not recommended for all patients, the test is suggested for some groups based on certain guidelines. The test should be considered for patients with unexplained difficulty in breathing or recent worsening of heart failure. It can also be considered to check patients who have a heart murmur. Additionally, the test should be used to check patients known to have severe heart valve problems.
The final test is non-invasive stress testing. This test measures how the heart functions under stress. It has been found that patients with stress-induced heart problems are more likely to have serious heart events in the future. However, the test is not recommended for all patients. According to guidelines, doctors could consider this test for patients who are having major surgery, who have decreased function of the heart, or if the doctor suspects a problem that could require changes to the treatment plan. For these patients, the stress can be caused by exercise or using drugs that make the heart work harder.
How is Cardiac Risk Assessment performed
In 1977, Goldman and his team created a system to measure the risk of heart complications during and after surgery. The system, known as the Cardiac Risk Index (CRI), used factors such as heart sounds, previous heart attacks, heart rhythm, age, type of surgery, and overall health condition to calculate the risk. Each factor was assigned a number of points, and the total points helped determine the potential risk.
In 1986, Detsky and his team updated Goldman’s CRI, making changes to the risk factors and adding chest pain, also known as angina. In 1996 and 2002, the American College of Cardiology and American Heart Association Taskforce updated the guidelines for assessing heart risks before non-heart-related surgery.
Nowadays, there are three accepted tools for calculating the risk of serious heart events during or after surgery: the Revised Cardiac Risk Index (RCRI), the National Surgical Quality Improvement Program Myocardial Infarction and Cardiac Arrest (NSQIP MICA) calculator, and the National Surgical Quality Improvement Program risk calculator.
The RCRI, developed by Lee and his team in 1999, is an updated version of Goldman’s CRI and the most commonly used risk calculator. It uses the same scoring system but includes six clinical factors: coronary heart disease, heart failure, stroke, severe diabetes, kidney problems, and the risk level of the surgery. The risk of serious heart events for each score was recently updated in 2019 to better reflect the actual risk. A score of 2 or higher indicates a higher risk.
The NSQIP MICA, created by Gupta and his team in 2007, uses data from hundreds of US hospitals to calculate the risk of heart attack and cardiac arrest. It includes factors such as the type of surgery, overall health, kidney function, anesthesiologist’s physical status classification, and age. This model was found to be more accurate than the RCRI.
Finally, in 2013, the NSQIP Surgical Risk Calculator was designed to perform a surgery-specific risk calculation. It’s an online calculator that collects 21 patient-related factors and finds out the risk of suffering a heart attack or cardiac arrest.
What Else Should I Know About Cardiac Risk Assessment?
It’s very important to check the heart health of patients before they go through any non-heart-related surgery. This is because a lot of people (32-69% of patients) may suffer a heart attack during or after their operation, which could lead to death. By checking their heart health beforehand, doctors can adjust their treatment plan and the type of anesthesia used during surgery. This helps to make sure the patient’s body can handle the stress brought on by the surgery.
