Always bind the grade to artery and timepoint. It describes epicardial contrast flow only; mechanism, tissue perfusion, clinical risk and management are separate outputs.
{
"categories": [
{
"outcome_code": "0",
"original_name": "no_perfusion",
"distal_penetration": "none_beyond_the_point_of_occlusion",
"distal_bed_opacified": "no"
},
{
"outcome_code": "1",
"original_name": "penetration_without_perfusion",
"distal_penetration": "contrast_passes_beyond_the_obstruction",
"distal_bed_opacified": "not_completely_before_contrast_hangs_up"
},
{
"outcome_code": "2",
"original_name": "partial_perfusion",
"distal_penetration": "contrast_passes_the_obstruction",
"distal_bed_opacified": "complete",
"entry_or_clearance": "perceptibly_slower_than_the_same_vessel_proximal_to_the_obstruction_or_a_comparable_uninvolved_bed"
},
{
"outcome_code": "3",
"original_name": "complete_perfusion",
"distal_penetration": "complete",
"distal_bed_opacified": "complete",
"entry_and_clearance": "as_prompt_and_as_rapid_as_the_proximal_or_comparable_uninvolved_bed"
}
],
"applicability": {
"use_for": "Qualitative description of epicardial coronary contrast flow in one named artery or treated branch on invasive coronary cineangiography.",
"classification_unit": "one_named_coronary_artery_or_target_branch_at_one_explicit_procedural_timepoint",
"required_inputs": [
"artery_and_target_lesion",
"angiographic_timepoint",
"antegrade_contrast_beyond_obstruction",
"complete_distal_bed_opacification",
"relative_speed_of_distal_entry",
"relative_speed_of_clearance",
"adequacy_of_injection_and_cine_run",
"intervention_state",
"residual_stenosis_thrombus_dissection_spasm_or_distal_embolization",
"collateral_flow_recorded_separately"
],
"outside_scope": [
"noninvasive_coronary_CT_or_MR_flow_grading",
"TIMI_risk_score_for_STEMI_or_NSTE_ACS",
"TIMI_myocardial_perfusion_grade",
"myocardial_blush_grade",
"corrected_TIMI_frame_count_as_if_it_were_the_same_variable",
"cerebral_mTICI_reperfusion",
"mechanism_or_treatment_selection_from_grade_alone"
]
},
"classification_algorithm": [
{
"priority": 1,
"if": "no_antegrade_contrast_beyond_the_obstruction",
"output_code": "0"
},
{
"priority": 2,
"if": "contrast_passes_beyond_obstruction_but_fails_to_opacify_the_entire_distal_coronary_bed",
"output_code": "1"
},
{
"priority": 3,
"if": "entire_distal_bed_opacifies_but_entry_or_clearance_is_perceptibly_delayed",
"output_code": "2"
},
{
"priority": 4,
"if": "entire_distal_bed_opacifies_and_both_entry_and_clearance_are_as_prompt_as_normal_reference",
"output_code": "3"
},
{
"priority": 5,
"if": "injection_cine_duration_or_reference_is_inadequate_to_distinguish_the_boundary",
"output": "ungradable_or_bounded_grade_with_reason"
}
],
"angiographic_quality_and_timepoint_gate": {
"required_technical_context": [
"cine_frame_rate",
"projection",
"catheter_engagement",
"contrast_volume_and_force_when_available",
"absence_of_damping_or_reflux_that_invalidates_comparison",
"run_continues_through_clearance",
"heart_rate_when_quantitative_timing_is_used"
],
"timepoint_examples": [
"before_wire",
"after_wire_crossing",
"after_balloon",
"after_stent",
"end_of_PCI",
"specified_minutes_after_fibrinolysis",
"follow_up_angiography"
],
"timepoint_rule": "A pre-intervention and post-intervention grade are different observations. Never overwrite the initial grade with the final grade or report a bare TIMI number without its artery and timepoint.",
"collateral_rule": "Collateral filling is recorded separately and does not convert absent antegrade culprit flow into TIMI 2 or 3.",
"technical_failure_rule": "Selective injection artifact, catheter damping, severe ostial disease, short cine acquisition or noncomparable reference flow can make the grade unreliable; state the limitation instead of manufacturing grade 3 or calling no-reflow."
},
"original_definition_and_three_cycle_guard": {
"original_grade_3": "Grade 3 requires distal entry as prompt as proximal or uninvolved flow and clearance just as rapid; it is a normal-reference comparison, not merely passage within an arbitrary duration.",
"invalid_shortcut": "Do not define grade 3 as opacification within fewer than three cardiac cycles. The 1999 TIMI analysis found that this shortcut classified 66.8 percent versus 57.3 percent by the original definition in the compared trials, an approximately 10 percentage-point overcall.",
"three_cycle_context": "In normal arteries dye transit averaged about 0.93 cardiac cycles and none exceeded three in the method-drift analysis; three cycles was roughly six standard deviations above normal.",
"agent_rule": "If a source uses the three-cycle convention, label it as a nonoriginal convention and do not silently harmonize it to original TIMI grade 3."
},
"corrected_TIMI_frame_count_companion": {
"purpose": "CTFC is a separate continuous and more objective measure of epicardial flow that can refine heterogeneous visual grades; store it alongside, not inside, the ordinal grade.",
"method": "Count cineframes from the first frame in which dye fully enters the artery and moves forward to the frame in which dye reaches the standardized distal landmark, normalized for acquisition frame rate.",
"LAD_correction": "The original normal LAD count was 36.2 plus or minus 2.6 frames, approximately 1.7 times the RCA and circumflex; divide LAD frame count by 1.7 to obtain the corrected LAD count.",
"original_normal_reference_at_30_fps": {
"corrected_mean": "21.0_frames",
"RCA": "20.4_plus_or_minus_3.0",
"LCx": "22.2_plus_or_minus_4.1",
"LAD_uncorrected": "36.2_plus_or_minus_2.6"
},
"frame_rate_guard": "The published values were derived at 30 frames per second. Normalize other acquisition rates before comparison and preserve the vessel-specific distal landmark and count method.",
"non_equivalence": "A CTFC value does not automatically assign a visual TIMI grade, and a visual grade 3 does not prove a normal CTFC."
},
"distinct_measures_and_name_collisions": {
"epicardial_TIMI_flow": "This 0-3 system assesses contrast movement through an epicardial coronary artery.",
"TMPG_or_myocardial_blush": "TIMI myocardial perfusion grade and myocardial blush grade assess tissue-level contrast appearance and washout. Microvascular obstruction can persist despite TIMI 3 epicardial flow.",
"TIMI_risk_scores": "The STEMI and NSTE-ACS TIMI risk scores combine clinical variables and are unrelated outputs despite sharing the acronym.",
"mTICI": "Modified Treatment in Cerebral Infarction grades percentage reperfusion of a downstream cerebral territory after stroke treatment. Its 0-3 labels and the phrase penetration without perfusion must never be converted to coronary TIMI flow.",
"stenosis_and_FFR": "Anatomic residual stenosis, pressure-derived physiology and coronary flow reserve answer different questions and must be returned separately."
},
"mechanism_and_no_reflow_boundary": {
"grade_is_phenotype": "TIMI grade reports observed flow, not its cause. Low flow can reflect persistent epicardial obstruction, thrombus, dissection, spasm, distal embolization, microvascular obstruction, competitive or collateral flow, hemodynamics or technical injection factors.",
"no_reflow_guard": "Post-PCI TIMI less than 3 without residual mechanical obstruction can support a no-reflow phenotype, but the mechanism must be assessed before the term is used; pre-wire TIMI 0 is not automatically no-reflow.",
"grade_3_guard": "TIMI 3 is normal epicardial flow by the original visual definition but does not establish normal myocardial perfusion, absence of infarction, successful complete revascularization or clinical stability."
},
"management_boundary": {
"acute_context": "The 2025 ACS guideline bases urgent management on the ACS syndrome, symptoms, ECG, biomarkers, hemodynamics, anatomy, complications and revascularization context; a TIMI grade is one procedural observation.",
"low_flow": "TIMI 0-2 during or after intervention prompts the operator to identify a mechanical, thrombotic, vasomotor, embolic, microvascular or technical explanation, but the grade itself does not select another wire pass, thrombectomy, stent, vasodilator, antithrombotic agent or surgery.",
"grade_3": "Grade 3 is the desired epicardial-flow state in reperfusion studies, not a discharge criterion and not a reason to omit tissue-perfusion, residual-lesion, ECG, ventricular-function or clinical assessment.",
"universal_rule": "Never generate medication doses, device steps, procedural termination, transfer or discharge from the grade alone."
},
"risk_and_prognosis_boundary": {
"historical_association": "Lower or incomplete post-reperfusion TIMI flow has been associated with worse group outcomes and grade 3 with better outcomes in historical reperfusion cohorts, but the effect depends on artery, timepoint, treatment era, shock, infarct size and tissue perfusion.",
"no_fixed_percentages": "Do not attach the old GUSTO or other cohort mortality percentages to an individual grade as a personal probability, and do not pool grades 0-1 or 2-3 unless the cited study prespecified that grouping.",
"tissue_level_residual_risk": "Patients can have microvascular obstruction and adverse outcomes despite TIMI 3 epicardial flow; integrate myocardial perfusion, ST resolution, ventricular function and clinical status when those questions are asked."
},
"agent_output_contract": [
"Return artery, lesion or branch, projection and explicit pre/post-intervention timepoint with every grade.",
"Return whether contrast crosses the obstruction, whether the complete distal bed fills, and whether both entry and clearance match the reference.",
"Return injection/cine adequacy, collateral flow, residual stenosis, thrombus, dissection, spasm, embolization and suspected no-reflow mechanism separately.",
"If CTFC is measured, return raw frames, frame rate, distal landmark, vessel and LAD correction separately from the visual grade.",
"Keep epicardial TIMI flow, tissue-level TMPG or blush, TIMI clinical risk score, physiology and cerebral mTICI in separate named fields.",
"State uncertainty or a bounded grade when the grade-1/2 or grade-2/3 boundary cannot be observed.",
"Never infer treatment, infarct size, myocardial salvage, prognosis or procedural success from the numeral alone."
],
"missing_input_behavior": [
"If the artery or timepoint is missing, do not return an unqualified TIMI number.",
"If the cine run stops before distal clearance, grade 3 cannot be confirmed; return grade 2 versus 3 or ungradable.",
"If distal bed completeness is unknown, do not distinguish grade 1 from grade 2 with false certainty.",
"If only a three-cardiac-cycle statement is available, preserve that convention and do not call original grade 3.",
"If tissue perfusion is not assessed, say not assessed rather than normal because epicardial flow is grade 3.",
"If mechanism is unknown, report low flow without labeling thrombus, no-reflow or spasm."
],
"supporting_sources": [
{
"role": "original_four_grade_definition",
"citation": "TIMI Study Group. N Engl J Med. 1985;312:932-936",
"doi": "10.1056/NEJM198504043121437"
},
{
"role": "quantitative_companion",
"citation": "Gibson et al. Circulation. 1996;93:879-888",
"doi": "10.1161/01.CIR.93.5.879",
"pmid": "8598078"
},
{
"role": "grade_3_method_guard",
"citation": "Gibson et al. Am Heart J. 1999;137:1179-1184",
"doi": "10.1016/S0002-8703(99)70380-7",
"pmid": "10347349"
},
{
"role": "current_ACS_care_boundary",
"citation": "Rao et al. JACC. 2025",
"doi": "10.1016/j.jacc.2024.11.009"
}
],
"source_locator": "TIMI Study Group 1985, DOI 10.1056/NEJM198504043121437, original phase-I four-grade definitions; Gibson et al. 1996, DOI 10.1161/01.CIR.93.5.879, CTFC method and normal vessel references; Gibson et al. 1999, PMID 10347349, original grade-3 wording and three-cycle overcall; 2025 ACC/AHA/ACEP/NAEMSP/SCAI ACS guideline, DOI 10.1016/j.jacc.2024.11.009, current management context."
}