Primary prevention defibrillators in clinical practice

Introduction: Guidelines for primary prevention of sudden cardiac death (SCD) advocate implantable cardioverter defibrillator (ICD) therapy in patients with reduced left ventricular ejection fraction (LVEF). Many patients are not considered for treatment and the net benefit of ICDs in real life is insufficiently studied.

The aims of these studies were to investigate compliance to guidelines and to study the balance between benefits and complications of ICD therapy.

Methods and Results: Paper I. In a retrospective study of the medical records of 187 patients with acute myocardial infarction (AMI), with LVEF ≤35%, we evaluated the decision process behind ICD treatment. Inadequate follow-up according to guidelines was found in 32% of the patients, while 41% showed an improvement in LVEF to such a degree that an ICD was no longer indicated.

Paper II. A prospective study of 100 patients with AMI and reduced LVEF (≤40%). The incidence and time span of improvement of LVEF were studied. At one month of follow-up, 55% of the patients had an LVEF of >35%. The mean difference in LVEF between one and three months was small (1.9 percentage units). A high risk of life-threatening arrhythmias (9%) was found in the first few weeks after AMI.

Paper III. Using register data, 865 patients with reduced LVEF treated with ICDs for primary prevention of SCD were identified. The medical records were scrutinized. We found that annually 6% of the patients had correctly treated arrhythmias, 2.4% had inappropriate shocks and 4.4% had complications requiring reoperation. Men were twice as likely to receive correct ICD treatment compared with women.

Paper IV. We analyzed intracardiac electrograms from 125 explanted ICDs from deceased patients. During the last 24 h of life, 31% of the patients had received shock treatment. Although 52% of the patients had a do-not-resuscitate order, 65% of them still had ICD shock therapies activated.

Conclusions: Follow-up after AMI is insufficient. Most patients show improved LVEF after AMI and in the majority the improvement can be confirmed after one month, implying that further delay of ICD implantation may not be motivated. Patients (especially men) with heart failure benefit from ICD treatment, but complications are common and it is crucial to inactivate shock treatment towards the end of life.

List of scientific papers

I. Primary prevention of defibrillator implantation after myocardial infarction: clinical practice and compliance to guides. Sjöblom J, Ljung L, Frick M, Rosenqvist M, Frykman-Kull V. Europace. 2012; 14:490-5.
https://doi.org/10.1093/europace/eur354

II. Early identification of ICD candidates after acute myocardial infarction. Sjöblom J, Muhrbeck J, Witt N, Alam M, Frykman-Kull V. [Submitted]

III. Efficacy of primary preventive ICD therapy in an unselected population of patients with reduced left ventricular ejection fraction. Sjöblom J, Kalm T, Gadler F, Ljung L, Frykman-Kull V, Rosenqvist M, Platonov PG, Borgquist R. [Submitted]

IV. Implantable defibrillator therapy before death: high risk for painful shocks at end of life. Kinch Westerdahl A, Sjöblom J, Mattiasson A-C, Rosenquist M, Frykman V. Circulation. 2014 Jan 28; 129(4):422-9.
https://doi.org/10.1161/CIRCULATIONAHA.113.002648