REVIEW A Review on Advanced Atrioventricular Block in Young or Middle-Aged Adults S ´ ERGIO NUNO CRAVEIRO BARRA, M.D., RUI PROVID ˆ ENCIA, M.D., M.Sc., LU ´ IS PAIVA, M.D., M.Sc., JOS ´ E NASCIMENTO, M.D., and ANT ´ ONIO LEIT ˜ AO MARQUES, M.D. From the Cardiology Department, Coimbra Hospital and University Centre, Centro Hospitalar de Coimbra, Coimbra, Portugal Complete atrioventricular block is a relatively uncommon arrhythmia that is nonetheless increasingly seen in elderly people of developed countries, due to the increase in life expectancy. Congenital and degenerative etiologies are the most commonly seen among young and old patients, respectively. However, scientific literature is surprisingly scarce regarding the etiology of complete atrioventricular block in the asymptomatic otherwise healthy young and middle-aged adult population. Coronary artery disease, autoimmune disorders such as systemic lupus erythematosus or rheumatoid arthritis, history of acute or chronic infectious or hypersensitivity myocarditis, infiltrative processes, hypothyroidism, congenital cardiopathies such as left ventricular noncompaction or Ebstein anomaly, lamin A/C mutations, and pathologic hypervagotony and idiopathic degenerative scleroatrophy of the atrioventricular junctional specialized tissue (Lenegre-Lev disease) are among the most frequent etiologies of complete atrioventricular block in young or middle-aged adults. To our knowledge, no comprehensive review on the specificities of the investigation warranted in this age group has ever been developed, nor have the implications of particular diagnoses on treatment modalities been appropriately addressed. We aim at reviewing the most frequent differential diagnoses of advanced atrioventricular block in otherwise healthy asymptomatic or mildly symptomatic young or middle-aged adults and their impact on therapeutic options. Additionally, we suggest a diagnostic algorithm that may be helpful in this group of patients. (PACE 2012; 00:1–11) complete atrioventricular block, atrioventricular block etiology, cardiac conduction Introduction Complete heart block, also referred to as third- degree heart block or third-degree atrioventricular (AV) block, is a disorder of the cardiac conduction system where there is complete dissociation of the atrial and ventricular activity due to the absence of conduction through the atrioventricular node (AVN) or His-Purkinje system. Although Mobitz I second-degree AV block is observed in 1–2% of healthy young people, especially during sleep, the prevalence of third-degree AV block is only 0.02% in the United States and 0.04% worldwide. 1,2 Its incidence increases with advancing age (highest in people older than 70 years), despite an early peak in infancy and early childhood due to congenital Conflicts of interest: None. Financial support: None. Address for reprints: S´ ergio Nuno Craveiro Barra, M.D., R. Ant ´ onio F. Fiandor 112 – 4 Dto, 4430–017 V. N. Gaia, Portugal. E-mail: sergioncbarra@gmail.com Received March 27, 2012; revised May 12, 2012; accepted June 11, 2012. doi: 10.1111/j.1540-8159.2012.03489.x complete AV block. This latter form of heart block occurs in one out of each 20–22,000 births, usually associates with maternal antibodies to Ro (SS-A) and La (SS-B) and maternal lupus, and shows a 60% female preponderance (against a 60% male preponderance for acquired complete heart block). 3 Acquired AV block results from various pathologic states causing infiltration, fibrosis, or loss of connection in portions of the healthy conduction system. The underlying condition strongly influences both the age of presenta- tion/onset and the prognosis. To the best of our knowledge, no comprehensive review on the specificities of the investigation warranted in oth- erwise healthy young or middle-aged adults with complete asymptomatic or mildly symptomatic AV block has ever been developed, nor have the implications of particular diagnoses on treatment modalities been appropriately addressed. Thus, this review presents a description of the most frequent differential diagnoses and etiologies of complete AV block in young or middle- aged asymptomatic adults and describes their impact on subsequent therapeutic measures. In addition, the authors suggest a potential diagnostic algorithm for this group of patients. C 2012, The Authors. Journal compilation C 2012 Wiley Periodicals, Inc. PACE, Vol. 00 2012 1