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Commentary

Case 1- A 79 years old male who underwent coronary arterybypass surgery about 8 months back wants to undergo cataractextraction.

Case 2- A 55 years old woman with no history of hypertension, diabetes and coronary artery disease has T wave inversion in leadsV1-4. She wants to undergo laparoscopic cholecystectomy.

Case 3- A 45 years old labourer who has broken his left leg bonesneeds an orthopaedic surgery. There is no significant medical history.

Case 4- A 29 years old woman with severe mitral stenosis withruptured ectopic pregnancy.

In present day practice of anaesthesia as well as cardiology, wefrequently come across such patients who are suffering from cardiacdisorder or suspected to have one and want to undergo non-cardiacsurgery. Practitioners from both the fields are perplexed by similarkind of questions like how far should we investigate? How muchrisk is actually there? How to reduce that risk? etc. Despite recentpublication of guidelines by American as well as English cardiacauthorities, the percolation of exact practical information to thepracticing physician is woefully little.

What is the approach suggested by guidelines? Howmeaningful it is?

The first thing that should be evaluated at the onset is the urgencyof surgery. Emergency surgeries for conditions, which threaten life or limb like exploratory laprotomy for hemoperitonium, caesareansection for foetal distress, ruptured ectopic pregnancy, crush injuriesof limbs, vascular injuries etc. should be taken up without any delay.In such cases, assessment of perioperative risk of cardiac event shouldbe done after the surgery and appropriate measures should be taken.

If patient is known to have a cardiac disorder, the severity ofthe disease should be evaluated. Any patient with symptomaticsevere valvular stenosis or regurgitation, symptomatic heart failure,acute coronary syndrome and uncontrolled rhythm disorder (activecardiac condition) should ordinarily be not taken up for surgery.Such patients require detailed assessment of their cardiac conditionby a cardiologist and decision for surgery should be taken accordingly[1,2].

In a rare case, when a patient with active cardiac condition comesfor an emergency surgery, decision for surgery should be taken onindividual basis weighing risk of surgery against the conservativemanagement [1,2].

Next step in evaluation is to ascertain if there is pre-existingcoronary artery disease or any other cardiac disorder. One musttake history and perform physical examination diligently for thispurpose. This is the key area where we usually underperform andlater on face multiple problems. Check, all the records that areavailable, howsoever, irrelevant they appear to the patient. Examinecarefully for any signs of heart failure, presence of cardiac murmursand additional sounds. This will prevent many surprises in operationtheatre.

Patients with proven cardiovascular disease should be referred to a cardiologist for assessment of current status. They shouldbe managed as per the existing guidelines for particular cardiaccondition. The perioperative management should be guided as perthe detailed guidelines on the subject, a brief summary of which willfollow in this document.

If there is no documentary or historical evidence of cardiacdisease, ascertain the risk of surgery. Traditionally it is divided intothree categories (low, intermediate and high), details of which canalso be found in detailed guidelines [1,2]. Patients undergoing low risksurgery need no further evaluation, once an active cardiac conditionis ruled out. However, their future risk of cardiovascular events maybe evaluated separately by the physician and advised accordingly.

Thereafter exercise capacity of the patients, who are undergoingintermediate to high risk surgery, should be determined. There is a setof questions, which can be used to determine the exercise capacity ofthe patient and can be individualised as per the social circumstances.Following list provides such a set of activities where exercise capacityof individual can be ascertained [1-3].

Ability to dress without stop 2-2.3 METs

Ability to clean windows- 3.7METs

Ability to mop floor- 4.2 METs

Hang Washed clothes- 4.4 METs

Have shower without stop – 3.6-4.2 METs

To climb two flight of stairs without stop at normal pace- More than 4 METs

Can have Sexual intercourse without stop- 5-5.5 METs

Carry objects that are at least 80 pounds- 8 METs

Jog or walk 5 miles an hour- 9 METs

Carry at least 24 pounds up 8 steps- 10 METs

If a patient can perform at least 10 METs of exercise without any symptoms and there is no obvious cardiovascular abnormality as perhistory and examination, he/she may be subjected to almost all noncardiacsurgeries [1,4].

Patients with more than 4 METs of exercise capacity but lessthan 10 METs may require more objective evaluation dependingupon the risk of surgery and clinical probability of cardiac disease.The literature does not provide any definite approach towards thesepatients. In fact, the European and American guidelines also differ onthis issue. As per the American guidelines, further testing for patientswith exercise capacity between 4 to 10 METs may be foregone butit is a class IIb indication, which means insufficient evidence withdoubtful benefit [1]. On the other hand, European guidelines suggestproceeding with surgery in all those with exercise capacity of morethan 4 METs despite some reservations [2].

There are more angles to this tricky situation. The optimal exercisecapacity is different for different age groups and gender. For example,good exercise capacity for a 40 years old male will be ~ 10.0 METswhile it will be ~ 7.0 METs for a 60 years old female. Hence criteriaof 10 METs is not applicable to all patients. Every effort should bemade to decipher the cause, if a subject has lower than the expectedexercise capacity. One of the practical nomograms which can be usedto calculate good exercise capacity is -

For males- 14.7 - (Age x 0.11) METs

For Females- 14.7 - (Age x 0.13) METs

85% of the value derived in METs is considered just acceptable[5].

It is practically good to make a patient climb two flights of stairs without stop, at normal pace, in the health facility itself, if there is a doubt about their exercise capacity.

In view of uncertainties on this issue, we should evaluate exercise capacity of each patient carefully. Patients who have exercise capacity more than 4 METs and have no symptoms or clinical findingssuggestive of cardiovascular disease should ordinarily be subjected tosurgery without further testing [1,2].

Patients with exercise capacity less than 4 METs

The patient who has exercise capacity less than 4 METs andrequire intermediate to high risk surgery may be subjected to stresstesting. We do not have clear guidelines regarding who should besubjected to stress test and who should not be.

One of the approaches is to estimate the risk factors for perioperativeacute cardiac event. There are five clinical predictors as perrevised cardiac risk index (RCRI) [6]. These are

1. Angina pectoris or history of myocardial infarction

2. Kidney disease with GFR < 60 ml/ minute

3. Diabetes mellitus requiring insulin therapy

4. History of ischemic stroke or transient ischemic attack

5. History of heart failure in the past.

As per European guidelines, presence of three or more risk factorswarrant stress testing. It also states that stress testing may be used inany patient where it is likely to change perioperative management.However, these predictors were proposed about two decades backand can be considered as mere rough guides for clinicians today [2].In the current era, it will be difficult to clear a patient for surgery,both by cardiologist and anaesthetist, who is giving typical or classicalhistory of exertional angina with exercise capacity less than 4 METswithout subjecting him to further testing, even if it is the only riskfactor present, Hence, applicability of revised cardiac risk index isdebatable in current era.

This notion gets further support from American guidelines thathave dropped the recommendation of doing stress testing basedon number of clinical predictors in their latest edition. Rather, itrecommends stress testing only if it is likely to change perioperativemanagement, which may include changes in cardiac drug therapy,decision regarding revascularization and anaesthetic management[1].

There is more confusing data regarding the occurrence ofperioperative cardiac events in these patients with exercise capacityless than 4 METs. Wiklund et al. reported absence of any correlationbetween functional capacity as assessed in METs and perioperativeadverse cardiac events [7]. Another study on the issue claimed thatinability to climb two flight of stairs (attaining a height of at least 12 meters in 15 seconds) confers worse prognosis for patient undergoingthoracic surgery but has no negative implications for non-thoracicsurgeries [8]. Goswami et al. found partially or totally dependentfunctional status as a powerful predictor of intraoperative cardiacarrest and subsequent 30 days mortality [9].

Will subjecting all these patients to stress testing be beneficial?Coronary artery revascularization prophylaxis (CARP) study found that RCRI score accurately predicts occurrence of perioperative cardiac event, however revascularization prior to surgery was not able to reduce events in such patients except for patients with left main disease [10,11]. On the other hand, one of the studies involving patients undergoing vascular surgery demonstrated long-term benefit of routine preoperative angiography as compared to those undergoing angiography only after positive stress test. All patients inthis study had RCRI >2 [12]. However, current American guidelinesforbid use of routine coronary angiogram preoperatively [1].

What we can do in this subgroup?

We do not have clear, evidence-based recommendations fordealing with such patients where exercise capacity is less than 4METs. Subjecting all these patients to stress testing will neither becost effective nor it will result into definite reduction in cardiac eventsand long-term survival as per current evidence. A logical proposal is to treat each patient on individual basis. We must try to ascertainthe reason for low exercise capacity. All those patients where anginaor equivalent symptoms appear to be the cause of limitation may besubjected to stress testing. This should preferably be imaging basedexercise rather than pharamacological stress testing. All patients whohave breathlessness as the limiting cause of reduced exercise capacitymay be subjected to echocardiography (ECHO) and pulmonaryfunction testing. Those patients who may have structural heart diseasebased on clinical examination, electrocardiogram (ECG) or X-raychest should also be subjected to ECHO. Rest of the group whichwill include various causes of limited exercise capacity like obesity,anaemia, orthopaedic limitations, renal diseases etc may be subjectedto stress testing after calculating number of clinical risk factors (3 ormore risk factors) [2]. However, we must inform the patient as well asthe surgeon that these patients fall into a high risk group, whatever bethe result of stress testing.

The decision to revascularize patients from this subgroup shouldnot only be influenced by the current guidelines of coronary arterydisease but also by the fact that stenting with drug eluting stentswill render them ineligible for elective surgeries for a long duration;may be one year and revascularization may not reduce the rateof perioperative and long term cardiac events and death. In factguidelines clearly state that routine coronary revascularization beforenon-cardiac surgery should not be performed exclusively to reducethe risk of perioperative cardiac events [1,2].

How can we reduce the perioperative cardiac event rate ?

Can we really assess and prevent all cardiac events? The studiesinvestigating the perioperative acute myocardial infarction tell usthat prolonged ischemia with demand-supply mismatch and plaquedisruption with thrombus formation are two important mechanisms.Infarction without ST elevation with underlying prolonged ischemiais commoner than ST elevation infraction with plaque disruption[13-15]. We do not have a non-invasive test, which can predictplaque disruption with subsequent thrombosis accurately. Hence, wecannot predict a proportion of acute cardiac events in peri-operativeperiod by any means. Non-invasive testing, at best, can only provideinformation about existing significant flow-limiting lesions.

We can prevent prolonged ischemia mainly by keeping themyocardial demand in check. Mechanistically, it can be done wellby beta-blockers. However, role of beta-blockers in perioperativemanagement have become controversial in recent years [1,16].

Current guidelines recommend continuation of beta-blockers inpatients who are already taking it for a long time. It also recommendsstarting beta-blockers in patients with three or more risk factors fromRCRI or in those patients with long term indication of beta-blockerspreoperatively. This should not be done on day of surgery but at leastone day prior to surgery. Preoperative initiation of beta-blockers isa class IIb indication, indicating insufficient evidence and doubtfulbenefit. As per European guidelines, the agent of choice is eitherbisoprolol or atenolol [1,2,16].

Statins is another group of drugs that are found to be usefulin reducing cardiac events associated with non-cardiac surgery.However, currently they are indicated only in patients undergoing vascular surgery. They should be started at least 2 weeks prior to thesurgery. They are not recommended in other non-cardiac surgeries ifthere is no other indication for their use [1,2].

Summary of key recommendations concerning thepatients with proven cardiac disease before a non-cardiacsurgery [1,2]

Electrocardiogram (ECG) should be done for those with knowncardiac disease. It may also be done as a baseline for those withcardiac risk factors and need to undergo high-risk surgery. There is noconsensus regarding the prognostic value of various ECG changes atthe baseline. As a general rule, implication of these changes increasewith increasing age and number of coronary risk factors.

Role of stress testing has been discussed above. However, onemust keep in mind that image based stress testing has a far betternegative predictive value than positive predictive value in preoperativescenario.

Patients with suspected or proven heart failure should undergoechocardiographic evaluation before non-cardiac surgery. Inaddition to ECHO, natriuretic peptides may also be measured. Drugtherapy should be optimized and patient should be stabilised beforesurgery with beta-blockers, angiotensin converting enzyme (ACE)inhibitors, diuretics and mineralocorticoid antagonists. In case ofnewly diagnosed heart failure surgery should be deferred by at least3 months.

If patient is receiving angiotensin receptor blockers or angiotensinconverting enzyme (ACE) inhibitors, consider stopping them 24hours prior to surgery and should be restarted at the earliest possible.

Patients with newly diagnosed hypertension should be evaluatedfor end-organ damage and other cardiovascular risk factors.However, surgery should ordinarily be not deferred for hypertensiveswith blood pressure below 180/110 mmHg.

Major cardiac events after non-cardiac surgery are more commonin patients with prior cardiac events. Risk of perioperative strokeand mortality is high even up to 6 months after acute myocardialinfarction.

Asymptomatic patients who have undergone a cardiac by-passsurgery in last six years can be taken up for intermediate risk surgerywithout stress testing. However, baseline low ejection fractionremains a risk factor.

Elective non-cardiac surgery should not be performed in patientswith balloon angioplasty, bare-metal stents and drug-eluting stentsfor a period of 14 days, 30 days and 365 days respectively.

The decision to stop antiplatelet drugs in patients having a stentshould be discussed between surgeon, cardiologist and the patient. Ifsurgery requires P2Y12 inhibitors to be discontinued, aspirin shouldbe continued in peri-operative period and P2Y12 inhibitors restartedas soon as possible.

Aspirin may be continued (not started) in patients without acoronary stent only when risk of increased cardiac event is more thanrisk of bleeding.

Key points

- Patients who require emergency non-cardiac surgeryshould be taken up for surgery at the earliest. Diligent bed-sideclinical assessment regarding any cardiac disorder should be made.

- Every patient should undergo thorough and detailedhistory and bed-side clinical examination.

- Patient with active or acute cardiac conditions likesymptomatic severe valvular stenosis or regurgitation, acute coronarysyndrome, uncontrolled heart failure or uncontrolled rhythmdisorder should be referred for detailed cardiac evaluation prior tonon-cardiac surgery.

- Patient requiring low risk surgeries should go for surgeryin absence of active cardiac conditions without any further work-up.

- Exercise capacity should be ascertained in every individualbefore intermediate and high-risk surgery. Optimal exercise capacitydiffers with age and gender. Cause for suboptimal capacity should besearched for.

- Patients with good exercise capacity can be taken up forsurgery without further evaluation.

- Patient with suboptimal exercise capacity but with ability toperform more than four METs of exercise needs careful consideration.However, majority of them may also be taken up for surgery.

- Patients with less than 4 METs of exercise capacityconstitute a high risk group for perioperative cardiac eventsirrespective of results of further evaluation. However further testingneeds to be done for optimization.

- There is no consensus regarding the prognostic value ofvarious ECG changes at the baseline.

- Image based stress testing has a far better negative predictivevalue than positive predictive value in preoperative scenario.

- Use of routine coronary angiogram preoperatively isforbidden.

- Routine coronary revascularization before non-cardiacsurgery should not be performed exclusively to reduce the risk ofperioperative cardiac events.

- We cannot predict all the acute cardiac events in perioperativeperiod by any means.

- Preventive role of beta-blockers in perioperative settingis controversial. However, patients should be continued on betablockersif they are already receiving them.

- Elective non-cardiac surgery should be avoided for 6months after acute myocardial infarction. It should also be avoidedfor 12 months in those with drug-eluting stents.

- Low baseline ejection fraction remains a risk factor despitethe protective effect of CABG.