| Abbreviations | Meaning |
 | HEROICS | How Effective Are Revascularization Options In Cardiogenic Shock? [trial] |
 | HFECG | High Frequency Electrocardiography |
 | HHCS | High-altitude Hypertrophic Cardiomyopathy Syndrome |
 | HI-CPR | High-impulse Cardiopulmonary Resuscitation |
 | HIC-CPR | High-impulse Compression Cardiopulmonary Resuscitation |
 | HOC | Human Ovarian Cancer; Hydroxycorticoid; Hypertrophic Obstructive Cardiomyopathy |
 | HOCAP | Hypertrophic Obstructive Cardiomyopathy Ablation Pacing [study] |
 | HOCM | Hypertrophic Obstructive Cardiomyopathy |
 | HOCM | High-osmolar Contrast Medium; Hypertrophic Obstructive Cardiomyopathy |
 | HOMC | Hypertrophic Obstructive Cardiomyopathy |
 | HRE | Hepatic Reticuloendothelial [cell]; High-resolution Electrocardiography; Hormone Receptor Enzyme; Hormone Response Element |
 | HTCVD | Hypertensive Cardiovascular Disease |
 | IAC CPR | Interposed Abdominal Compression Cardiopulmonary Resuscitation |
 | IACD | Implantable Automatic Cardioverter-defibrillator; Intra-arterial Conduction Defect |
 | IC | Impedance Cardiogram |
 | ICARIS | Intervention Cardiology Risk Stratification [study] |
 | ICC | Interventional Cardiac Center |
 | ICCM | Idiopathic Congestive Cardiomyopathy |
 | ICD | Implantable-cardioverter Defibrillator |
 | ICD | Impedance Cardiogram |
 | ICD | Implantable Cardioverter-defibrillator |
 | ICD | Initial Cardioverter-defibrillator |
 | ICD | Intracardiac Defibrillator |
 | ICDC | Implantable Cardioverter-defibrillator Catheter |
 | ICDS | Integrated Child Development Scheme; International Cardiac Doppler Society |
 | ICE | Intracardiac Echocardiography |
 | ICECG | Intracardiac Electrocardiography |
 | ICF | International Cardiology Foundation |
 | ICG | Impedance Cardiogram; Impedance Cardiography; Indocyanine Green; Isotope Cisternography |
 | ICI | Intracardiac Infection |
 | ICIN | Intracoronary Streptokinase Trial Of The Interuniversity Cardiology Institute Of The Netherlands |
 | ICM | Intelligent Cardiovascular Monitor |
 | ICM | Isolated Cardiovascular Malformation |
 | ICO | Idiopathic Cyclic Oedema; Impedance Cardiac Output; Infection Control Officer |
 | ICR | Intracardiac Catheter Recording |
 | ICT | Intracardiac Thrombus |
 | ICVS | International Cardiovascular Society |
 | IDC | Idiopathic Dilated Cardiomyopathy; Infiltrating Ductal Carcinoma; Interdigitating Cell |
 | IDCS | Idiopathic Dilated Cardiomyopathy Study |
 | IECG | Intracardiac Electrocardiography |
 | IEGM | Intracardiac Electrogram |
 | IMAC | Intervention In Myocarditis And Acute Cardiomyopathy [study] |
 | IMEP | Investigation In Menopausal Women Of The Effect Of Estradiol And Progesterone On Cardiovascular Risk Factors |
 | IMPROVED | Influence Of Introduction Of Mycophenolate Mofetil And Reduction Of Cyclosporine On Renal Dysfunction After Cardiac Transplantation [study] |
 | INSPIRE | Increasing Participation In Cardiac Rehabilitation; Intravascular Ultrasound Study Predictor Of Restenosis [trial] |
 | IOE | Intraoperative Echocardiography |
 | ISC | International Society Of Cardiology |
 | ISCVS | International Society For Cardiovascular Surgery |
 | ISFC | International Society And Federation Of Cardiology |
 | J | A Reference Point Following The QRS Complex, At The Beginning Of The ST Segment, In Electrocardiography |