THICKEN, THICKEN, THICKEN, DROP: WENCKEBACH SECONDARY TO HYPERTROPHIC CARDIOMYOPATHY

ABSTRACT

TOPIC Cardiovascular Disease TYPE Medical Student/Resident Case Reports INTRODUCTION: Wenckebach is an atrioventricular conduction disorder leading to progressively lengthened PR interval followed by dropped beats. Hypertrophic cardiomyopathy (HCM) is a genetic cardiac muscle disease characterized by left ventricular hypertrophy that can cause symptoms that are typically categorized into those from heart failure, chest pain, or arrhythmias. HCM is rarely associated with AV blocks with few case reports describing a connection. We will present a case of second degree AV block Mobitz Type I known as Wenckebach block secondary to HCM. CASE PRESENTATION The patient is a 63-year-old woman with no significant past medical history reporting to the hospital for substernal chest pressure and lightheadedness. She was found to have symptomatic second degree AV block Mobitz Type I and was scheduled for dual chamber pacemaker. Prior to pacemaker implantation, echocardiogram was obtained that was concerning for left ventricular outflow tract obstruction and takotsubo cardiomyopathy. Left and right heart catheterization was performed that showed no significant coronary artery disease or takotsubo cardiomyopathy. Cardiac MRI was performed that showed features concerning for HCM. The patient underwent successful implantation of automatic implantable cardioverter defibrillator (AICD) with improvement in symptoms. Unfortunately, due to COVID-19 related limitations, further work up of HCM has been delayed including genetic testing. DISCUSSION: Wenckebach block is typically caused by myocardial ischemia, myocarditis, iatrogenic or cardiomyopathy of amyloidosis or sarcoidosis etiology. There is sparse literature discussing HCM causing first degree and complete heart block. Wenckebach block caused by HCM is very rare with only one other significant case found discussing the association. Once Wenckebach is discovered, a thorough work up for the underlying cause must be completed. In our case further work up via echocardiogram and cardiac MRI revealed HCM allowing for appropriate intervention with implantation of an AICD. CONCLUSIONS: Wenckebach block is rarely caused by HCM, but if obvious causes have been ruled out including myocardial ischemia, myocarditis, or iatrogenic then further work up is required. Cardiac imaging including echocardiogram and possibly cardiac MRI may be warranted to determine the underlying cause of the heart block, allowing for appropriate treatment. HCM is a rare cause of Wenckebach block, but must be considered on the differential diagnosis. REFERENCE #1 Wong TC. First-Degree Atrioventricular Block and Hypertrophic Cardiomyopathy "I Have a Bad Feeling About This". J Am Heart Assoc. 2020 Mar 17;9(6)e015911. doi 10.1161/JAHA.120.015911. Epub 2020 Mar 9. PMID 32146897;PMCID PMC7335525. REFERENCE #2 Dubey L, Guruprasad S, Bhattacharya R, Subramanyam G. Complete Heart Block in Hypertrophic Cardiomyopathy A Rare Association. Kathmandu Univ Med J (KUMJ). 2015 Oct-Dec;13(52)372-4. doi 10.3126/kumj.v13i4.16841. PMID 27423292. REFERENCE #3 Konishi E, Kawasaki T, Shiraishi H, Yamano M, Kamitani T. Additional heart sounds during early diastole in a patient with hypertrophic cardiomyopathy and atrioventricular block. J Cardiol Cases. 2015 Apr 1;11(6)171-174. doi 10.1016/j.jccase.2015.02.010. PMID 30546559;PMCID PMC6281973. DISCLOSURES No relevant relationships by Anas Ahmed, source=Web Response No relevant relationships by Rebekah Lantz, source=Web Response No relevant relationships by Mark Saling, source=Web Response No relevant relationships by Steven Young, source=Web Response