Variable Conduction System Disorders in Takotsubo Cardiomyopathy: A Case Series

Abstract

Takotsubo cardiomyopathy is an acute cardiac condition characterized by transient systolic dysfunction of the left ventricular apex and mid-ventricle. Documented EKG presentations for Takotsubo cardiomyopathy include ST-segment elevation or T-wave inversion. These EKG presentations are included in the diagnostic requirements for Takotsubo cardiomyopathy. This paper presents two cases of atypical EKG presentations, both conduction system disorders, and their possible mechanisms. Changes to the diagnostic criteria for Takotsubo cardiomyopathy should be considered to include these variant EKG presentations.

Introduction

Takotsubo cardiomyopathy (TCM) is classically characterized by transient systolic dysfunction of the mid-to-apical segment of the left ventricle mimicking myocardial infarction, but without obstruction of the coronary arteries. Typically, patients present with ST-segment elevation on EKG, elevated cardiac biomarkers, and apical ballooning shown on echocardiography or left ventriculography.¹ This paper describes two cases of atypical EKG presentations of TCM, both conduction system disorders. Each patient presented to Kuakini Medical Center in Honolulu with suspected acute myocardial infarction, but were diagnosed with TCM by cardiac angiography and left ventriculography.

Case Reports

Patient 1

An 80-year-old woman of Japanese ancestry with a history of atrial fibrillation, hypertension, hyperlipidemia, and pulmonary fibrosis was scheduled for elective right rotator cuff repair. The patient was anxious and uneasy during pre-operative right shoulder nerve block and suddenly complained of substernal chest pain and difficulty breathing. Rhythm on the monitor revealed monomorphic ventricular tachycardia. She also had elevated blood pressure. She was immediately intubated for airway protection, given esmolol for blood pressure control, and amiodarone for conversion to sinus rhythm. EKG at that time revealed new onset left bundle branch block (Figure 1). Creatine Kinase isoenzyme MB (CK-MB) levels remained within normal range, however troponin-I was elevated at 0.2 ng/mL (normal < 0.10 ng/mL) on admission and peaked at 0.35 ng/mL four hours later. She was immediately taken to the cardiac catheterization laboratory. There was no evidence of coronary artery disease, however ejection fraction was depressed at 40%. Left ventriculography was performed and revealed basal hyperkinesis with anterior dyskinesis and hypokinesis of the apex and base (ie, apical ballooning), consistent with TCM (figure 2). Her treatment was supportive and she was discharged five days later in good condition.

Figure 1.

EKG of patient 1 reveals new-onset left bundle branch block.

Figure 2.

Left ventriculography of patient 1 reveals hyperkinesis of the base while the remainder of the left ventricle is dyskinetic, giving the typical appearance of Takotsubo cardiomyopathy.

Patient 2

An 80-year-old woman of Japanese ancestry with history of dementia and hypertension presented to the emergency department with acute onset of chest pain associated with dyspnea. Two weeks prior to admission, the patient noted gradual onset of bilateral lower extremity edema. One week prior to admission, she noted occasional chest pressure without radiation lasting five to ten minutes, associated with intermittent palpitations. The patient's older sister passed away five months previously, leaving the patient as the last remaining sibling. Since then, she appeared depressed, had been eating less, and had decreased interest in her hobbies and activities. In the ER, the patient presented with a blood pressure of 220/62 and heart rate of 49. An EKG showed third-degree AV block and anteroseptal infarction (Figure 3). The patient's Troponin-I was elevated at 0.15 ng/mL (normal < 0.10 ng/mL) and peaked at 1.63 ng/mL four hours later. CK-MB was 2.8 ng/mL (normal < 5.0 ng/mL) at presentation but peaked at 9.3 ng/mL four hours later. Brain natriuretic peptide was also elevated at 807 pg/mL (normal < 100 pg/mL). Urgent cardiac catheterization was performed and coronary angiography showed no significant coronary obstructive lesions. However, left ventriculography showed apical ballooning, consistent with TCM (figure 4). A temporary transvenous pacemaker was placed at this time, and permanent pacemaker inserted the next day. The patient was started on a heart failure regimen. She was discharged to home four days after admission in good condition.

Figure 3.

EKG of patient 2 reveals new-onset third-degree AV block and anteroseptal infarction.

Figure 4.

Left ventriculography of patient 2 reveals apical ballooning, the typical appearance of Takotsubo cardiomyopathy.

Discussion

TCM was first described in 1991 in Japan and was named after the round-bottomed narrow neck Japanese fishing pot used for trapping octopus. It is also known as apical ballooning syndrome, broken heart syndrome, and stress-induced cardiomyopathy. As the latter two names indicate, TCM is frequently caused by intense emotional or physical stress, as seen in patient 1.¹ The exact pathophysiology of TCM is unknown, but the following has been proposed: multivascular coronary vasospasm, abnormalities in coronary microvascular function, and catecholamine-mediated cardiac toxicity.²

The vast majority of TCM patients are post-menopausal women. TCM most commonly presents as chest pain; however other symptoms include dyspnea, syncope, and shock. More serious complications include tachyarrhythmias and bradyarrhythmias, mitral regurgitation, cardiogenic shock, and heart failure. Troponin and CK-MB levels are elevated in 86.2% and 73.9% of patients, respectively.² EKG abnormalities are most commonly ST-segment elevation and T wave inversion, in 81.6% and 64.3%, respectively.² ST-segment elevation is thought to be due to the dyskinesis of the apical segment just as a left ventricular aneurysm may cause persistent ST-segment elevation.³

The recommended Mayo clinic diagnostic criteria for TCM include four requirements: “(1) Transient akinesis or dyskinesis of the left ventricular apical and mid-ventricular segments with regional wall-motion abnormalities extending beyond a single epicardial vascular distribution, (2) Absence of obstructive coronary disease or angiographic evidence of acute plaque rupture, (3) New EKG abnormalities (either ST-segment elevation and/or T-wave inversion) or modest elevation in cardiac troponin, and (4) Absence of pheochromocytoma or myocarditis.”⁴

These diagnostic criteria were developed from seven case series.^{1, 5–10} Although these studies mention that Takotsubo patients can present with non-ST elevation EKG changes, six of the seven studies^{1, 5–9} excluded patients that did not present with ST-elevation. Thus, non-ST elevation EKG changes such as conduction abnormalities were not fairly represented in creating the diagnostic criteria for Takotsubo cardiomyopathy.

As seen in the two patients presented in this paper, TCM can present as conduction abnormalities. Patient 1's EKG revealed left bundle branch block (LBBB) while patient 2's EKG revealed complete AV block. TCM uncommonly presents with LBBB, however it is estimated to occur in 9% of patients.¹¹ Even less common is complete heart block, seen in fewer than 5% of TCM patients.¹²

Mechanisms of TCM causing conduction system disorders have been proposed. First, the deterioration of blood flow secondary to left ventricular dyskinesia may decrease coronary blood flow to the conduction pathway. This may lead to conduction block.¹³ A second mechanism involves the catecholamine excess that is thought to trigger TCM. Catecholamines may induce coronary vasospasm, which decreases coronary blood flow to the conduction pathway (particularly the right coronary artery and its branches).¹⁴ A third mechanism proposes that continual ischemia may result in conduction pathway fibrosis, causing permanent conduction block. Additionally, age-related damage to the conduction pathways may be a contributing factor.¹²

Conclusion

ST-segment elevation and/or T-wave inversion are the EKG hallmarks of TCM and are part of the current recommended Mayo clinic diagnostic criteria. However, as seen in this paper, TCM can be diagnosed in cases that do not have these hallmark features. However, six of the seven studies used to originally create these diagnostic criteria only include EKGs with ST-elevation, despite mentioning a variety of EKG presentations. Perhaps it is time to expand the diagnostic criteria to include various EKG presentations, such as conduction abnormalities as seen in these two patients.

Conflict of Interest

None of the authors identify a conflict of interest.