Thrombus Formation Patterns in HeartMate II Continuous-Flow Left Ventricular Assist Devices: A Multifactorial Phenomenon Involving Kounis Syndrome?

Metallic devices are increasingly used in contemporary cardiological practice. They include coronary stents, artificial cardiac valves, bioprostheses for transcatheter aortic valve replacement, closure devices for patent foramen ovale and atrial septal defects, pacemakers, defibrillators, and left ventricular assist devices. Metals constitute the main components of these devices. Metal anions eluted from the components attached to circulating proteins can act as sensitizers able to induce hypersensitivity inflammation and thrombosis. Allergy to nickel occurs in up to one fourth of the population in several areas of the world and is the most frequent cause of allergic contact dermatitis. The HeartMate II device is made from titanium with ruby bearing. Titanium metal ions from HeartMate II are eluted through the action of blood, saline, proteins, and mechanical stress that can induce hypersensitivity and immune dysfunctions rendering titanium no longer biologically inert. An unexpected high rate of thrombosis with substantial morbidity and mortality has been observed with the use of this device, making the search of causality of thrombosis mandatory to predict and prevent this daunting complication. Although the cause of thrombosis seems to be multifactorial, careful history-taking regarding hypersensitivities, monitoring of inflammatory mediators, and lymphocyte transformation studies should be always performed in sensitive patients.