*2.2.1 Epidemiology*

Intracardiac device infections constitute approximately 10% of all endocarditis cases [24]. CIEDs have been implanted in patient as early as 1960s, but over the last two decades had significant increase in incidence. According to American Heart Association update, between 1997 and 2004, PPM placement increased by 19% and ICD placement increased by 60% [25]. Other studies quote an even higher increase of 30% for PPM and over 500% for ICDs [26]. In the United States greater than 500,000 PPMs and ICDs are implanted per year with over 4 million implanted between 1993 and 2008 [27]. Notably, more patients who are elderly and those with many comorbidities have been receiving these devices [25]. In developed countries 20–35% of CIEDs were placed in patients older than 80 years of age [25].

Over the years, changing the implantation site of ICD from abdomen (associated with 3.2% infection rate) to pectoral site (associated with 0.5% infection rate) initially decreased the incidence of device related infections [25]. Despite the innovation in PPM and ICD technology together with better surgical technique, the rate of infections associated with cardiac devices has increased by 124–210% [25, 26]. About 1.8–31.1 cases of CIED infection per 1000 device years has been reported for PPM and ICD devices and overall higher rates of infection with ICDs and CRTs [27]. This change is likely due to increased rate of CIED implantation in people over the age of 65 and presences of major comorbidities such as renal failure, respiratory failure, heart failure and diabetes [26]. CIED infections are associated with up to 18% of morbidity and mortality and increase by 47% per decade hospital charges [26].

Early infection typically arises from device implantation [27]. With first time implantation the rate of CIED related infection is 0.5–1% and 1–5% with device replacement or upgrade [27]. CIED related infection can involve the bloodstream, the generator pocket, the leads, or endocardial structures [26, 27]. Late infection typically arises from patient poor health or other clinically significant processes.

Almqvist et al., further divides the spectrum of CIED infections into six different categories: early post-implantation inflammation, uncomplicated pocket infection, complicated pocket infection, definite CIED lead infection, possible CIED lead infection, CIED-associated endocarditis, and probable CIED infection [26].
