title: Shortcomings of the Lown grading system for observational or experimental studies in ischemic heart disease.
abstract: The Lown grading system uses three levels of frequency and four complex features to grade ventricular arrhythmias. The seven Lown grades are mutually exclusive (a patient can be in only one grade) and hierarchical (higher grades indicate increased likelihood of death). We evaluated the ability of the Lown arrhythmia grading system to predict death in 400 patients who were convalescing from acute myocardial infarction. Lown grading produced a poor distribution among grades of the population, lacked a monotonic increase in risk with increasing arrhythmia grade, lacked a substantial risk gradient between grades, and showed a lack of isometry in the higher grades. Also, the Lown grading system thwarts the use of standard multivariate techniques for relating the frequency and characteristics of ventricular premature depolarizations (VPDs) to cardiac death. We also examined the utility of the Lown arrhythmia equation for evaluating the results of antiarrhythmic drug therapy. The Lown grading system failed to reveal clearly the change in VPD frequency and characteristics as a function of drug dose. We propose an alternative grading system that is not mutually exclusive or hierarchical. This grading system lacks many of the flaws of the Lown grading system and is suitable for standard multivariate analyses but, like the Lown grading system, still fails to show the relationships among ventricular arrhythmias, time, drug dose, and activity.
mesh_terms: D001145:Arrhythmias, Cardiac / Q000145:classification / Q000503:physiopathology; D003327:Coronary Disease / Q000145:classification* / Q000503:physiopathology; D004562:Electrocardiography; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D007099:Imipramine / Q000627:therapeutic use; D011153:Population; D011379:Prognosis; D012306:Risk; D013610:Tachycardia / Q000401:mortality
chemical_list: D007099:Imipramine