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The Ranjan Laboratory

The Ranjan Laboratory’s research focuses on exploring tissue and organ scale physiology and pathophysiology in various contexts including atrial fibrillation (AF), atypical left atrial flutter (ALAF), ventricular tachycardia (VT), and cardiac stereotactic radiotherapy (cSRT). We leverage a combination of cardiac computational modeling, machine learning, large animal experimental models, cardiac magnetic resonance imaging (cMRI), biochemical assays, cardiac electrophysiological mapping techniques, and human clinical data to explore disease progression, treatment strategies, and general cardiac physiology.

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A color-coded 3D map of the hearts left atrium (LA) and right atrium (RA) shows electrical activation times, ranging from 0 ms (red) to -150 ms (blue), with an inset highlighting a detailed region.

Featured Publications

Infographic explaining fibrillatory area (FA) as an arrhythmia predictor post ablation, with diagrams, FA calculation formulas, and two bar graphs comparing FA and scar area by recurrence status. Error bars denote standard deviation.Area Available for Atrial Fibrillation to Propagate Is an Important Determinant of Recurrence After Ablationhttps://pubmed.ncbi.nlm.nih.gov/33640348/This study leveraged patient specific computational models to robustly define and characterize the fibrillatory area hypothesis. This hypothesis postulates that in order for reentral activity to sustain in the atria, a certain amount of contiguous atrial tissue must be available, and barriers such as ablations which reduce this area can reduce the ability of the atria to sustain reentryKamali R, Kump J, Ghafoori E, Lange M, Hu N, Bunch TJ, Dosdall DJ, Macleod RS, Ranjan R. Area Available for Atrial Fibrillation to Propagate Is an Important Determinant of Recurrence After Ablation. JACC Clin Electrophysiol. 2021 Jul;7(7):896-908. doi: 10.1016/j.jacep.2020.11.008. Epub 2021 Feb 24. PMID: 33640348; PMCID: PMC9255558.
Rowed 3D heart models show mapped activation times and fibrosis scars during atrial arrhythmia cycles. Color bars indicate activation time and fibrosis percentage. Right shows anatomical mapping and scar areas.Case report: Personalized computational model guided ablation for left atrial flutterhttps://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2022.893752Using patient specific computational models, we simulated four cases of atypical left atrial flutter. These simulations produced reentrant circuits that matched those observed in clinical electrophysiological mapping. The simulation-predicted flutters were visualized and presented to clinicians. Validation of the computational model was motivated by recording from electroanatomical mapping. These personalized models successfully predicted clinically observed atypical flutter circuits and at times even better than invasive maps leading to flutter termination at isthmus sites predicted by the model.M. Lange, E. Kwan, D. J. Dosdall, R. S. MacLeod, T. J. Bunch, and R. Ranjan, “Case report: Personalized computational model guided ablation for left atrial flutter,” Frontiers in Cardiovascular Medicine, vol. 9, 2022, doi: 10.3389/fcvm.2022.893752. [Online]. Available:
Four 3D heart models: (A) shows healthy (black) and fibrotic (yellow) areas; (B) displays conduction speed (blue to red); (C) illustrates fractional anisotropy (black to yellow); (D) shows conduction heterogeneity (purple to yellow-green).Diffuse functional and structural abnormalities in fibrosis: Potential structural basis for sustaining atrial fibrillation https://doi.org/10.1016/j.hrthm.2024.10.060Using a combination of electroanatomical mapping and cardiac MRI analysis, we detailed the tissue and electrophysiologic changes that occur during the progression of atrial fibrillation in a large animal model. We found distinct differences in conduction velocity, conduction heterogeneity, and fractional anisotropy which correlated to tissue scale structural remodeling.E. Kwan, E. Ghafoori, W. Good, M. Regouski, B. Moon, J. M. Fish, E. Hsu, I. A. Polejaeva, R. S. MacLeod, D. J. Dosdall, and R. Ran- jan, “Diffuse functional and structural abnormalities in fibrosis: Potential structural basis for sustaining atrial fibrillation,” Heart Rhythm, 2024
Infographic showing high-density driver mapping, driver development tracking, recurrence data, and identified sites of driver recurrence in atrial fibrillation, with charts, heart diagrams, and annotated heatmaps.Are drivers recurring or ephemeral? observations from serial mapping of persistent atrial fibrillation
https://doi.org/10.1093/europace/euae269		In this study we characterized the recurrence of atrial fibrillation drivers longitudinally in a large animal model. We found that there were distinct driver locations in the atria which were observed across time.B. Hunt, E. Kwan, E. Paccione, B. Orkild, K. Yazaki, J. Bergquist, J. Dong, R. S. MacLeod, D. J. Dosdall, and R. Ranjan, “Are drivers recurring or ephemeral? observations from serial mapping of persistent atrial fibrillation,” EP Europace, vol. 26, no. 11, p. euae269, 10 2024. 

The Ranjan Lab Research Team

A man with short dark hair, glasses, and a mustache is wearing a white lab coat and patterned tie, looking directly at the camera with a neutral expression against a blurred background.

Dr. Ravi Ranjan, MD, PhD

EugeneKwan headshot

Dr. Eugene Kwan, PhD

JakeBergquist headshot

Dr. Jake Bergquist, PhD

SurachatJaroonpipatkul headshot

Ben Orkild

Eric Paccione

Bram Hunt

Rui Jin

Dr. Kyoichiro Yazaki, MD

Dr. Surachat Jaroonpipatkul, MD