Electrocardiographic changes after lung resection: Case report and brief review.

The incidence of acute coronary syndrome after a lung resection is less, especially in an asymptomatic patient. However, arrhythmias are very commonly encountered which can be benign or may require anti-arrhythmic agents thereby increasing stay postoperatively in the Intensive Care Unit. We encountered unexpected ST-T changes after a left upper lobectomy under general anesthesia in a 60-year-old lady in the immediate postoperative period that made us to review the literature for electrocardiographic abnormalities after lung resection surgeries.

INTRODUCTION

Fresh onset ECG changes in the post operative period always bothers the anaesthesiologist. The worry is even amplified if the fresh change is in the form of ST-T changes i.e. either ST elevation or ST depression. A coronary event has to be ruled out in these patients as all peri-operative events such as induction of anaesthesia, hemodynamic instability intra-operatively and surgical stress can lead to adverse cardiovascular events. We encountered ECG changes in the form of ST elevation which we investigated thoroughly. We searched Pubmed and Medline for case reports, case series or review articles describing ECG changes after lung surgeries.

CASE REPORT

A 60-year-old female patient with fibrocavitatory disease involving left lung was scheduled to undergo a left upper lobectomy of the lung under general anesthesia. She was a nonhypertensive, nondiabetic lady with no history suggestive of coronary artery disease. Electrocardiogram (ECG) at rest was normal [Figure 1]. During her cardiovascular work up, she was advised an exercise stress test that was negative for inducible ischemia. She achieved a heart rate of 150/min and had no ST-T changes, arrhythmias or desaturation during the test.

Figure 1

Preoperative normal 12 lead electrocardiogram

After confirming nil by mouth status and checking for consent, patient was shifted to the operation room. Monitors (pulse oximeter probe, lead II and V5 ECG) was attached and an arterial cannula for beat to beat monitoring of arterial blood pressure (BP) was inserted in the right radial artery. An epidural catheter was placed in T7-8 interspace prior to induction under local anesthesia under strict asepsis, and catheter was kept 5 cm in the epidural space. General anesthesia was induced with 2 mg midazolam, 100 μg fentanyl, 100 mg propofol and 6 mg vecuronuim and trachea intubated with a 35 Fr left sided double lumen tube which was confirmed in supine and right lateral position with an intubating bronchoscope. Anesthesia was maintained with 1 L oxygen, 1 L medical air, propofol infusion (100–200 μg/kg/min) and dexmedetomidine infusion at 30 μg/h that is, 0.7 μg/kg/h. Left lateral open thoracotomy was under general anesthesia with one lung ventilation in right lateral decubitus position. Left upper lobectomy was performed, and the defect due to lobectomy was closed with a serratus anterior and intercostal muscle flap. Blood loss was around 500 mL. We decided to ventilate the patient in the Surgical Intensive Care Unit (SICU) as the surgery went on for >6 h leading to core hypothermia (35°C) detected with a nasopharyngeal temperature probe placed in the left nostril. On shifting the patient to SICU, an abnormal ST segment was observed on the monitor. Her heart rate was 68/min, and arterial BP was 160/80 mmHg. A 12 lead ECG was ordered which revealed ST segment elevation in leads I, II, III, aVF, V4–6 [Figure 2, ECG done immediately after shifting the patient to SICU]. We started nitroglycerin infusion at 2.5 μg/min, administered 300 mg aspirin via Ryle's tube after discussing with the surgeon and 6 mg morphine intravenously considering it to be an acute coronary syndrome (ACS). We ordered an arterial blood gas, a hemogram (consisting hemoglobin, packed cell volume, total leucocytic and platelet count), serum electrolytes, chest radiograph and quantitative troponin T. All investigations were within normal limits, except troponin T that was 0.799 ng/ml that is, positive. We requested the cardiologist to perform a two-dimensional echocardiogram who informed us that there is a minimal pericardial effusion without tamponade. There was no left ventricular regional wall motion abnormality, biventricular function was normal, inferior vena cava was noncollapsible. The ECG done after 6 h was devoid of ST-T changes; however, there were low voltage complexes [Figure 3, ECG done 6 h after shifting the patient to SICU]. Later, the surgeon also informed us that the effusion could be possible due to handling of pericardium during surgery. ECG was done daily for 5 days as suggested by the cardiologist with the same machine, which showed no ST elevation.

Figure 2

Electrocardiogram showing ST elevation in leads I, II, III aVF,V4–6

Figure 3

Electrocardiogram after 6 h with low voltage complexes and no ST-T changes

DISCUSSION

After lung resection, the anatomy in the thoracic cage including mediastinum changes. This change may be reflected in the ECG as a new onset change that may be alarming ST-T changes. Usually, there is left axis deviation after a left sided lobectomy or left pneumonectomy. Left axis deviation can be a new finding after major lung resection or due to possible elevation of the diaphragm due to the space created after a lobe or lung resection. A new onset incomplete right bundle-branch block is also a common ECG finding after a pneumonectomy. Chhabra et al. had described ECG changes suggestive of acute anteroseptal myocardial infarction (MI) after left lung resection possibly due to mediastinal shift.[1] The overall incidence of MI reported after lung resection is 1.5–5%.[2]

Arrhythmias are the most common ECG abnormalities seen after lung resections, especially after pneumonectomy or upper lobectomy. Atrial fibrillation is the most common arrhythmia encountered perioperatively. The proposed reasons are damage to the cardiac plexus or damage to pulmonary vein during dissection or after ligation while operating at hilum as proximal trunks of pulmonary Vein's are myocardial sleeving that possess electrical properties. Increased vagal tone, inflammation of atrium, pulmonary hypertension, dilation of the right side of the heart and hypoxemia occurring perioparatively could be contributors to arrhythmia.[3] Prophylactic use of anti-arrhythmics is controversial as it doesn’t make sense to start it in anticipation.

Elderly patients, surgery for lung malignancy and pneumonectomy are the risk factors responsible for atrial fibrillation postoperatively.

In case of a proven ACS confirmed with increased troponins, symptomatic patient, abnormal ECHO findings along with new onset ST-T changes (ST elevation or non ST elevation), the patient should be managed as American College of Cardiology/American Heart Association guidelines by involving a cardiologist. Antiplatelets or heparin should be started in indicated patients if not contraindicated (increased surgical blood loss, frank blood in chest drain, dropping hemoglobin).[45] Statins, beta-blockers, nitrates should be promptly started.

Frye and Sahn reviewed preoperative and postoperative ECGs of 15 patients who underwent pneumonectomy and observed ECG changes suggestive of acute cor pulmonale in one-third patients possibly due to shift of QRS axis and precordial rotation on side of pneumonectomy.[6] Postpneumonectomy, the ECG picture may be variable and confusing suggestive of pulmonary embolism, massive MI, pericarditis or pericardial effusion although atrial arrythmias especially atrial fibrillation is the most common rhythm disturbance. ECG changes in pericardial effusion are nonspecific and insensitive.[7] However, a change of voltage from normal to low should raise a suspicion and echocardiography should be advised for confirmation and quantification.

In this patient, the ECG changes got reverted after 6 h possibly because many factors were rectified. The patient was warmed with warming blanket, analgesia was optimized with epidural infusion and morphine and possibly the pericardial effusion started resolving.

CONCLUSION

Anesthesiologists should be aware of the possible ECG changes due to lung resection owing to the anatomical changes that occur due to removal of lobes of lung or a whole lung per se We suggest to get a 12 lead ECG after every noncardiac thoracic surgery. New onset ST-T changes should be investigated. Whenever in doubt, a two-dimensional echocardiogram should be requested to know the function of the heart and to rule out acute ischemic events.