Cardiac Assessment
The main cardiac issues for a lung surgeon are ischaemia, failure and pulmonary hypertension. Despite the reputed high incidence of cardiac events following lung surgery, we have a relatively low incidence of peri-operative infarction (due to attention to hypotension, oxygenation and sputum retention), a seemingly inevitable incidence of supraventricular arrythmias with minimal associated morbidity and a tacit denial of right ventricular failure, often masquerading as acute lung injury.
Preoperative cardiac assessment is an inexact science and one only understood by your colleague thoracic surgeons and experienced thoracic anaesthetists.
Beware: A cardiologist may state that a patient is fit for anaesthetic or for an operation. This does not mean the patient is fit for a lung resection where postoperative hypoxaemia can be predicted, along with pericardial irritation, vagal nerve dissection, mediastinal shift, increased sympathetic tone associated with pain, and increased stress on the right ventricle. Neither is being fit for cardiac surgery the same as being fit for lung resection. After CABG or valve surgery cardiac function should actually be improved rather than the impairment of cardiorespiratory function associated with lung resection.
Ischaemic heart disease
All lung cancer patients (the 90% who have smoked) have ischaemic heart disease (IHD), whether they are aware of it or not. The anaesthetist will assume this and adjust his anaesthetic accordingly. The surgeon also needs to take this into account. The patient’s other disabilities such as COPD or arthritis may limit their activity to the extent that they don’t expose their IHD. Claudication or previous TIA’s will also point to latent coronary disease.
Perioperative re-infarction risk CHECK this data
If there has been a previous MI, the estimated risk of re-infarction following non-cardiac thoracic and vascular surgery is 6%. The mortality of these MI’s is 50%. This compares to a “normal” risk of 0.15%, though the latter is increased in the presence of angina, Q waves, CCF and diabetes. The risk is higher if there is an infarction in the six weeks prior to surgery, the risk thereafter reducing with time. However, a potentially curable tumour should be considered for resection at around six weeks as the balance of risk versus tumour advancement
Patients with poorly perfused areas of myocardium run the risk of further infarction during the procedure with arrhythmia (including ventricular fibrillation) or low output cardiac failure. An area of infarction per se has relatively low risk of causing these complications unless there are peri-infarction areas of ischaemia. Established areas of infarction may however, contribute to left ventricular compromise which may njot tolerate the fluid shifts associated with major lung resection.
The presence of IHD is an independent predictor of benefit from prophylactic minitracheostomy. IHD patients do not tolerate hypoxia or pulmonary sepsis and even minor degrees can induce catastrophic cardiac events. Therefore the evidence suggests that patients with a history of IHD should have a prophylactic minitracheostomy (Bonde2.pdf).
Clinical - The questioning is similar to that for exercise capacity. Make sure that the chest pain they are talking about is not pleurisy related to consolidated lung, chest wall pain due to invasion (not in itself a contraindication to surgery) or the burning pain of gastro-oesophageal reflux
Electrocardiogram - will give a static picture of (severe) previous coronary events, dysrhythmias and ventricular hypertrophy. The presence of Cor Pulmonale is usually a complete contraindication for a thoracic procedure.
Exercise Stress Treadmill (EST) - ECG is a static investigation which commonly underestimates the degree of IHD; stressing the heart can unmask latent IHD. The most straightforward means of stressing the heart is exercise, usually on a standardised protocol. A cardiopulmonary stress test (CPEST) gives more information than a standard cardiac exercise stress test (EST) in those being assessed for lung surgery. However, if the patient has minimal lung disease and a major cardiac co-morbidity, we may ask for a pure cardiac EST. Interpretation follows similar criteria to CPEST. Our anaesthetists are now at the stage of requesting a treadmill on ALL patients who have ischaemic heart disease (and an echocardiogram on those with history of infarction.)
Thallium stress test
Patients who are not able to exercise may be suitable for a Thallium stress test. Again the aim is to determine whether there are any potentially ischaemic areas of myocardium.
• if a reversible defect is demonstrated (i.e. ischaemia, potentially unstable), the risk of cardiac complications is 20 - 30%,
• if there is a fixed defect (i.e. already infarcted), the risk is lower at 2%.
If significant evidence of IHD is seen on EST, CPEST, or thallium, coronary angiography may be indicated.
Coronary Angiography
Patients with documented IHD should have their medication optimised to reduce the risk of perioperative events. B Blockers should be continued, and consideration given to commencing them a number of weeks prior to surgery. Where there is still symptomatic angina and re-vascularisation can be considered, coronary angiography is indicated. What amounts to “symptomatic angina” and what needs angiography can be difficult to call.
Cardiac Failure
A history of cardiac failure is usually a contra-indication to surgery unless it was associated with a specific cardiac event (AMI, SVT, PE, valve disorder) which has since been corrected or from which there has been full recovery.
Clinical - symptoms of current cardiac failure are more worrying. Orthopnoea, paroxysmal nocturnal dyspnoea (PND), raised JVP, ankle swelling, the need for a diuretic (other than an an anti-hypertensive dose of bendrofluazide. Beware of the patient on 40mg Frusemide “the doctor gave it to me when my breathing was bad”.)
Beware also of assessing a patient sitting in bed on a medical ward. On one hand you will not see him walking into the clinic on his own or being pushed in a wheelchair (wheelchairs contra-indicate virtually all intrathoracic procedures!) On the other hand, looking grey and emaciated in his pyjamas one may underestimate a patient’s performance status.
Echocardiogram - for most situations a transthoracic echocardiogram will give an indication of valve disease and an approximation of left ventricular function. Though not as accurate as a left ventriculogram at catheterisation, it will either clear the patient for surgery or indicate whether catheter is required. Echo may also give an indication of pulmonary hypertension.
Coronary angiography - ventriculography at the time of angiography gives a more accurate left ventricular ejection fraction.
Right ventricular failure - in pulmonary surgery it is right ventricular failure which kills, more than left. None of the above modalities adequately assesses right ventricular function and none can predict the strain that a pneumonectomy will place on the right ventricle. In addition to the peri-operative mortality of lung resection, there is an excess of non-cancer deaths in the first 6 months after surgery (particularly following pneumonectomy). Most of these are cardiac deaths, usually right ventricular in origin. Most get admitted to a medical ward with “chest infection” or to the hospice with “lung cancer”!
Pulmonary hypertension
The presence of established pulmonary hypertension is a contra-indication to virtually all thoracic procedures. Having said that, I suspect that a mild, sub-clinical degree of pulmonary hypertension may well pre-condition the right ventricle, allowing it to take the strain of a pneumonectomy or even LVRS
