Background: The precise relationship between increased thrombolysis in myocardial infarction (TIMI) frame counts and the topographical extent of isolated coronary artery ectasia (CAE) has not been fully explained. New parameters of linear dimension (LD) and the estimated ectatic area (EEA) together with the diameter and ectasia ratio may be associated with the corrected TIMI frame count (CTFC) in isolated CAE patients. Methods: The topographical parameters of ectatic coronary arteries and/or segments of 77 isolated CAE patients were consecutively studied. The CTFC for each coronary artery was determined by angiographic frame count. Results: Right coronary artery (RCA) was the most frequently affected. The RCA and left circumflex (LCX) had significantly longer LD (p < 0.001 for both), and greater EEA (p < 0.001 for both) than those of left anterior descending artery (LAD). Similarly, the RCA and LCX have higher CTFCs (p = 0.001 and p = 0.008, respectively) than LAD. All topographic parameters and CTFCs were positively correlated with Markis classification. Linear regression analyses revealed that CTFCs were strongly correlated with diameter, LD, ectasia ratio and EEA, while EEA was the best predictor for the CTFC. Among multiple linear and nonlinear regression models, the cubic model between the CTFC and EEA exhibits the best Goodness-of-Fit. Conclusion: The severity of the topographical extent of CAE was significantly correlated with increased CTFCs. Both the linear dimension and ectatic diameter (combined as EEA) were important for evaluating decreased coronary flow in isolated CAE patients.