Ejection Fraction (EF) – is the amount of blood pumped out of the heart’s main pumping chamber (i.e., the left ventricle) with each heartbeat, expressed as a percent of the volume of blood inside this chamber at the start of the beat. The heart normally ejects about 55-70% of the blood in its ventricle with each contraction. People with CHF and weak heart muscle will typically have an EF less than 45-50%.
QRS Complex – the sharp peak on an electrocardiogram (ECG, a recording of the heart’s electrical activity) that corresponds to the electrical activity generated when the muscles of the ventricles become activated and start contracting. Normally, the duration of the QRS complex is less than 120 millisecond, indicating that the entire heart muscle becomes activated within 120 millisecond. In many patients with heart failure, the QRS complex becomes abnormally long; indicating that it takes much longer to activate all of the heart’s muscles and the contraction becomes dyssynchronous. In such cases, a treatment called “cardiac resynchronization therapy” (CRT, described below) may be indicated.
Cardiac Resynchronization Therapy (CRT) - also referred to as biventricular pacing, is a form of therapy for CHF in which a specialized pacemaker is used to re-coordinate the action of the right and left ventricles. CRT is indicated for CHF patients that suffer from cardiac dysynchrony characterized by a prolonged QRS duration.
Implantable Cardioverter Defibrillator (ICD) - devices that monitor the heart for potentially dangerous types of contraction patterns, such as ventricular fibrillation (when the heat muscles contract in a completely chaotic manner so that no blood is pumped) or tachycardia (when the heart beats very fast). When an ICD detects such a rhythm, it delivers electrical shocks to try and restore normal contractions. ICDs are important for prolonging life in some patients with heart failure, but do not treat heart failure as they do not help to improve a patient’s quality of life or exercise tolerance.
Minnesota Living with Heart Failure Questionnaire (MLWHFQ) – a heart failure specific questionnaire filled out by patients, that includes 21 questions selected to be representative of the ways heart failure can affect the key physical, emotional, social and mental dimensions of quality of life. The patients grade each question on a scale of 1 to 6; 1 for good quality of life, and 6 for poor quality of life. The grades are used to create a global index of quality of life. The MLWHFQ is used to quantify a patient’s quality of life and to track changes in quality of life in response to treatment.