Preventing heart complications during surgery

 

It is recommended that those who have an increased risk of heart disease should undergo non-invasive assessment prior to surgery.

 

Almost everyone will undergo some form of surgery at some point in time. Heart events account for  a major percentage of complications during and after surgery. According to the article "Vascular Events In Non-cardiac Surgery Patients Cohort Evaluation (VISION) Study Investigators" carried in the Journal of the American Medical Association in 2012, almost 2 in 100 died within 30 days after surgery. If there is a heart attack during the surgery, the 30-day death rate can increase significantly to 17 per 100.

 

Predisposing causes

There are many reasons for the aggravation of underlying heart disease or triggering of a heart attack during surgery. Patient-related factors include underlying anaemia (resulting in less oxygen), impaired heart pump function and the discontinuation of anti-platelet medication in those who have had stents (cylindrical meshes) in their heart arteries.

 

Even for seemingly innocuous and minor surgeries, the consequences can be devastating. Mr A  had impaired heart pump function and had a longstanding groin hernia. During surgery he developed heart failure and by the time his heart doctor was called to assist, it was too late.

 

Madam B had a stent implanted in her left main heart artery  which was the  main supply of blood to the left pumping chamber of the heart. Her gynaecologist advised her to undergo minor cervix surgery and stopped her blood thinning medication pre- and post-surgery without discussing it with her heart doctor. She developed a massive heart attack resulting from clot formation in the left main artery stent and died.

 

Mr C had been on blood thinner to prevent blood clot formation in the heart due to an abnormal heart rhythm called atrial fibrillation (AF). In AF, blood clots can form spontaneously in the heart chamber and travel to the brain to cause a massive stroke. His surgeon advised him to stop his medication and proceeded with prostate surgery. Post-surgery, he developed a sudden massive stroke and subsequently died.

 

When undergoing general anaesthesia, the commencement of anaesthesia can result in a drop in blood pressure. Complications during surgery or bleeding during surgery can aggravate an underlying heart condition. Post-operative dehydration and inflammation can create an environment in which the blood is more prone to clot.

 

Guidelines

The 2014 American Heart Association (AHA)/American College of Cardiology (ACC) Guidelines on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Non-cardiac Surgery recommend that those who have an increased risk of  heart disease or have poor functional capacity should  undergo non-invasive assessment prior to surgery.

 

Most commonly, a 12 lead electrocardiogram (ECG) which is an electrical recording of the heart, is routinely performed before any surgery. For those who have shortness of breath or impaired heart function, an ultrasound of the heart to assess the heart pump function  will allow doctors to take the necessary precautions and ascertain the risks. For those with poor or uncertain functional capacity, the guidelines do recommend the use of treadmill testing combined with ultrasound of the heart (stress echocardiography) or nuclear scan of the heart (myocardial perfusion scan).

 

Abnormal results strongly predict post-operative complications. Increasingly, non-invasive assessment of the heart arteries using coronary computed tomographic angiography (CCTA) is being used by many physicians for those suspected to have underlying heart artery disease. This involves 3 dimensional X-ray imaging of the heart arteries which can be done on an outpatient basis.  CCTA  is especially useful for older patients who have limited functional capacity as the test can be done within seconds at rest.

 

Previous stenting

For those who have stents placed in their heart arteries, elective non-heart surgery should be delayed for at least 30 days after bare metal stent (BMS) implantation. For those with drug-eluting polymer coated metallic stents (DES), elective non-heart surgery should be delayed for at least 1 year after implantation of the DES. Where the surgery is necessary, the risk of clotting of the heart stent after stopping blood thinning medications must be weighed against the risks of further delay of the surgery.

 

If the non-heart surgery is not urgent and can be deferred, it should not be performed within 30 days after BMS implantation or within 12 months after DES implantation in patients in whom blood thinning medication must be stopped for the surgery.

 

A few of the new generation stents show virtually complete coverage of the stent struts by a new layer of cells in the arterial wall by 6 months after implantation of the stent.  Stents which are completely made of absorbable polymer should completely disintegrate by 2 to 3 years after stent implantation. For these new generation stents, cessation of blood thinning medication may be possible after complete stent strut coverage or complete absorption of the polymer stent.

 

Medications to start or avoid

A retrospective study of more than 200,00 patients  by Lindenauer published in the Journal of the American Medical Association in 2004 showed that those given cholesterol lowering medication (statin) in the first 2 days of hospitalization had significant reduction in death rates.   Present guidelines do recommend the commencement of statin  for patients undergoing surgery of vessels who are also at risk of heart disease  and have increased surgical  risk. As statins are well tolerated and have a proven safety record, there are more pros than cons to commence patients on statin.

 

The use of beta-blockers is uncertain as the data from the effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery trial (POISE trial) published in the Lancet journal in 2008 showed that it was associated with a higher incidence of all-cause mortality.  For those who have been on prolonged usage or have significant heart artery disease, the medication can be given.  However, current guidelines state that beta-blockers should not be started on the day of surgery. Furthermore, beta-blockers should be avoided or used with caution in those with slow heart rate or poor heart pump function.

 

For patients undergoing total hip or knee replacement, thinning of blood with low molecular weight heparin injection can reduce the risk of blood clot formation in the leg veins by about 35%. If these clots travel by the veins into the heart, they can potentially be life threatening.

 

Minimising risks

Taking the right precautions can help you minimise the risks of surgery. Key precautionary measures include :

 

• Always consult your heart specialist before undergoing surgery;

 

• Ensure that the surgeon and the anaesthetist have understood from your heart specialist your medical condition.

 

• If you have no known heart disease but have risk factors for heart disease  or have poor functional capacity, besides doing an ECG, a proper heart assessment such as stress echocardiography, stress myocardial perfusion scanning or CCTA should be considered before embarking on surgery.

 

• If you have severe heart disease, correct any underlying anaemia, avoid excessive lowering of blood pressure during anaesthesia, continue with statin medication and involve your heart specialist in the provision of medical care.

 

• If you have impaired heart pump function or a history of heart failure as in Mr A’s case, it is essential that you are not to be given excessive fluid infusion during surgery, and an ultrasound study of the heart should be done to assess the severity of heart impairment.

 

• If you had heart stents implanted, never stop your blood thinning medication without consulting the heart specialist even if other doctors tell you that it is safe to do so as in Madam B’s case.

 

• If you have the abnormal heart rhythm,  AF,  you must consult your heart specialist before stopping blood thinning medication. Failing to manage the situation optimally can lead to a massive stroke as in Mr C’s case.

 

Hence, even if you have underlying heart disease, you can go for your surgery with ease of mind and minimal surgical risks if you inform your heart doctor and take the precautionary measures.

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