European Journal of Cardiovascular Medicine

The coronary arteries form the principal source of blood supply to the myocardium, ensuring continuous perfusion to the heart throughout life. Despite their small caliber, their anatomical configuration and branching relationships determine both normal physiological function and the pattern of ischemic disease when pathology develops. Knowledge of their variations is therefore not merely of academic interest—it is fundamental to safe surgical, interventional, and diagnostic cardiovascular practice[1,2]. In the classical arrangement, the right coronary artery (RCA) arises from the anterior (right) aortic sinus, while the left coronary artery (LCA) originates from the left posterior aortic sinus. The LCA typically divides into the left anterior descending (LAD) and left circumflex (LCx) arteries, supplying the anterior and lateral walls of the left ventricle respectively. Together, these vessels provide end-arterial territories with limited collateral potential, making the understanding of their origin, course, and dominance pattern clinically critical[3,4]. However, anatomical studies have consistently shown that coronary architecture is far from uniform. Variations may involve the site or number of ostia, ostial height relative to the sinutubular ridge, branching pattern (bifurcation, trifurcation, or quadrifurcation), termination sites, and dominance distribution. Each of these features bears potential procedural implications—ranging from catheter selection and graft design to the interpretation of angiograms and surgical planning for valve or aortic root operations[5,6].

Embryologically, the coronary arteries develop from endothelial buds on the aortic root that establish connections with the peritruncal vascular plexus. Minor disturbances during this process can result in ectopic origins, high take-off positions, or accessory ostia. Similarly, variable fusion of subepicardial channels explains the spectrum of ramus intermedius, duplicated LAD, and myocardial bridging patterns observed in adult anatomy. These variations are generally asymptomatic but can become critical when superimposed disease or interventional manipulation is involved. For instance, a high take-off RCA may elude catheterization or cause myocardial ischemia during cardiac surgery if unrecognized; a short left main trunk complicates stent deployment; and myocardial bridging can mimic dynamic coronary obstruction on imaging. Contemporary cardiac imaging—computed tomography (CT) angiography and coronary magnetic resonance angiography—has made it possible to visualize these variations in vivo. Yet, cadaveric studies remain the definitive reference standard for defining precise anatomical relationships, verifying morphological measurements, and correlating imaging findings with true gross anatomy[7,8]. They provide an irreplaceable perspective on vessel topography, branching morphology, and dominance pattern across different populations and ethnic groups, aspects that remain underrepresented in imaging-based datasets. Previous studies have largely been restricted to small sample sizes or have focused on isolated parameters such as ostial location or dominance alone. Few have combined origin, morphometry, branching architecture, variant features, and dominance correlations within a single dataset. Moreover, regional studies from the Indian subcontinent are limited, despite known population-specific differences in coronary morphology that may influence the interpretation of angiographic norms and surgical outcomes[9,10].

Hence, the present investigation was undertaken to provide a comprehensive morphometric and morphological analysis of the coronary arteries in eighty formalin-fixed human cadaveric hearts. The study systematically documented the origin, number, and position of coronary ostia in relation to the sinutubular ridge; evaluated morphometric parameters such as the lengths and diameters of the right coronary artery (RCA), left coronary artery (LCA), left anterior descending artery (LAD), left circumflex artery (LCx), and posterior descending artery (PDA); examined the branching patterns and variant features including the presence of ramus intermedius, high take-off RCA, duplicated LAD, and myocardial bridging; and identified the termination sites of the RCA and LCx with corresponding dominance patterns. Special emphasis was placed on analyzing the correlation between coronary termination and dominance to validate internal anatomical consistency. By delineating these parameters and quantifying their variability, this study aims to establish a reliable anatomical baseline for the Indian population and to enhance the precision of coronary interventions, bypass graft planning, and radiological interpretation in both diagnostic and interventional cardiology.

Study design and setting

We conducted a cross-sectional, descriptive anatomical study on human cadaveric hearts to document coronary origin, ostial position, branching architecture, morphometry, termination, and dominance. Specimens were obtained from routine adult cadaver donations at the Department of Anatomy, Government Erode Medical College, the study was approved/exempted by the Institutional Ethics Committee, identifying information (age/sex identifiers beyond broad categories) was retained.

Specimen accrual and eligibility

• Sampling frame: Consecutive embalmed adult cadaveric hearts available during the study period (n = 80).
• Inclusion criteria: Adult hearts with intact aortic root, atrioventricular (AV) and interventricular (IV) grooves; adequate tissue preservation.
• Exclusion criteria (a priori): (i) prior cardiac or aortic surgery, (ii) penetrating/blunt cardiac trauma, (iii) gross malformation or destructive pathology of the aortic root/cusps, (iv) incomplete fixation or decomposition, (v) valve prosthesis, stents, or marked post-mortem artefact that precluded accurate measurement.

Preparation, fixation, and handling

All hearts were removed en bloc during routine dissection, rinsed, and fixed in 10% neutral-buffered formalin for ≥2 weeks. Before dissection, each specimen was soaked in running water to remove surface fixative, then placed on a padded dissection board in anatomical orientation. The aorta and pulmonary trunk were transected ~3 cm above the cusps to expose sinuses and the sinutubular ridge. Visceral pericardium and epicardial fat were gently reflected to reveal epicardial vessels.

Dissection protocol

Using fine scissors and blunt micro-dissection under adequate lighting:

1. Aortic root survey: The right/anterior, left posterior, and right posterior aortic sinuses were inspected for coronary ostial number and location; ostial height was referenced to the sinutubular ridge.
2. Right coronary artery (RCA): Traced from ostium along the AV groove to its termination; acute marginal and sinoatrial nodal branches documented.
3. Left main (LCA): From ostium to first division; downstream LAD (anterior IV groove) and LCx (left AV groove) followed to terminations; ramus intermedius/median artery noted when present.
4. Posterior mapping: Course to posterior interventricular sulcus and the artery giving rise to the posterior descending artery (PDA) identified (to classify dominance).
5. Variants: Accessory ostia, left conus from aorta, duplicated LAD, myocardial bridging (tunneled LAD segment) and high take-off RCA were recorded if present.

Operational definitions (pre-specified)

• Ostial position vs sinutubular ridge:
• Below: ostial lip entirely within the sinus, below the ridge crest;
• At: tangent to the ridge crest;
• Above: any portion above the crest.
• High take-off RCA: ostium located >3 mm above the ridge.
• Branching pattern (LCA):
• Bifurcation: LAD + LCx;
• Trifurcation: LAD + LCx + ramus intermedius;
• Quadrifurcation: LAD + LCx + ramus + median/intermediate artery.
• Diagonal branches: discrete epicardial diagonals from LAD (septal perforators excluded).
• Termination sites:
• RCA: (i) between crux–obtuse margin, (ii) acute–crux, (iii) posterior interventricular sulcus, (iv) obtuse margin;
• LCx: (i) crux–obtuse margin, (ii) posterior septum (as posterior interventricular/pseudo-PDA), (iii) obtuse margin.
• Dominance: artery giving rise to the PDA beyond the mid-posterior IV sulcus: right, left, or balanced (both contributing).

Measurements and instruments

• Lengths (RCA, LAD, LCx, PDA): traced along epicardial course using non-stretch surgical tape/thread, then measured on a millimetre scale (cm precision).
• Left main trunk length: ostial lip to first division (mm).
• Diameters (proximal): measured with a digital Vernier caliper (accuracy 0.01 mm) at the ostium or the first straight proximal segment (LAD/LCx).
• Ostial height: vertical relation to the ridge by visual alignment with a straight probe and ruled scale; high take-offthreshold as above.
• Each value was recorded twice by the primary observer; if discrepancy exceeded 5%, a third measurement was taken and the median retained.

Data management and quality assurance

Data were recorded on a pre-coded sheet and double-entered into a spreadsheet with range checks and logic rules (e.g., LCA bifurcation cannot co-exist with quadrifurcation). A 10-specimen subset underwent blinded re-measurement by a second anatomist to estimate inter-observer agreement (categorical features targeted for κ; continuous for ICC); disagreements were resolved by consensus at a third sitting.

Statistical analysis

Continuous variables are summarised as mean ± SD with observed range and 95% CI of the mean. Proportions are presented with Wilson 95% CIs.

• Paired comparison of ostial height (below vs not-below) across RCA vs LCA: McNemar test.
• Associations (e.g., posterior termination vs dominance): Fisher’s exact test (two-sided).
• No multiplicity adjustment was planned (single cohort, anatomical endpoints).
  Analyses were performed using standard statistical routines; p < 0.05 was considered significant.

Ethical considerations

The work used cadaveric material for anatomical research. All procedures complied with institutional policies and national guidelines on human tissue research. No clinical data were collected; privacy and dignity of donors were respected throughout.

Figure 1. Workflow of the Cadaveric Heart Study

This color-coded workflow illustrates the sequential stages of the study—from specimen screening and preservation to anatomical dissection, morphometric measurement, data validation, and statistical analysis. Blue boxes represent collection and fixation, yellow boxes denote dissection and mapping, green boxes show measurement and variant recording, orange boxes correspond to data processing and statistical evaluation, and purple boxes indicate reporting and result synthesis. Red highlights excluded specimens that failed eligibility criteria. Together, the diagram provides a visual overview of the structured, stepwise methodology applied to all 80 cadaveric hearts analyzed in this study.

Origin, Number, and Position of Coronary Ostia (n = 80)

We quantified ostial origin, multiplicity, and vertical height relative to the sinutubular ridge—features that influence catheter engagement and aortic root surgery. (Table 1)

Table 1. Origin, Number, and Position of Coronary Ostia (n = 80)

1. Accessory ostia typically supplied conus or sinoatrial (SA) nodal branches.
   c. Percentages computed from n = 80; minor rounding differences may occur.
   † McNemar test used because RCA and LCA positions are paired within the same hearts; continuity correction applied.

RCA origin was uniform (100% anterior aortic sinus), with rare LCA ectopy (2.5% from the right posterior sinus; 95% CI 0.7–8.7%). Multiple RCA openings were frequent (27.5%), and most ostia lay below the sinutubular ridge (RCA 88.7%, LCA 83.7%). The paired comparison of “below vs not-below” showed no significant side-to-side difference (McNemar p=0.13), while ostial multiplicity exhibited greater heterogeneity on the right (CV 43% vs 31%).

Morphometric Parameters of Major Coronary Arteries:

We quantified lengths and proximal diameters of the principal epicardial vessels to benchmark anatomic variability relevant to angiography, CABG planning, and stent sizing. (Table 2)

Table 2. Morphometric Parameters of Major Coronary Arteries (n = 80)

1. Lengths measured along the anatomic course (RCA from ostium to termination; LCA trunk from ostium to first branch point; LAD/LCx from bifurcation; PDA in posterior IV sulcus). Diameters measured proximally (ostium/segment just distal to origin).
   b. 95% CI of mean = mean ± 1.96 × (SD/√n) with n = 80. CV = coefficient of variation = SD/mean × 100%. c. Descriptive comparisons across vessels are provided; no paired hypothesis testing was performed because per-heart raw measurements were not analyzed here. d. Units: lengths in cm except LCA trunk in mm; diameters in mm.

Length hierarchy: RCA is longest (10.2 cm), followed by LAD (8.6 cm), LCx (7.3 cm), then PDA (6.1 cm). On average, RCA is ~18.6% longer than LAD, and LAD is ~17.8% longer than LCx, shaping graft reach and catheter working lengths.

Left main (LCA trunk) variability: Despite a modest mean (5.3 mm), the CV is highest (50.9%) with a wide 2–14 mm range—indicating frequent short trunks that can limit ostial/proximal stent landing zones and demand precise guide positioning.

Diameter hierarchy: LCA > RCA > LAD > LCx proximally; LCA is ~8.9% larger than RCA on average, informing guide size/graft calibration.

Precision: Narrow CIs for means (e.g., LAD length 8.2–9.0 cm, RCA diameter 4.4–4.6 mm) support stable central estimates for procedural planning.

Branching Pattern and Variant Arterial Features

Left main branching architecture, LAD diagonal distribution, and uncommon variants with 95% CIs for planning angiography/CABG. (Table 3)

Table 3. Combined Summary of Branching Pattern and Variant Features (n = 80)

1. Branching pattern defined at the left main bifurcation: bifurcation (LAD+LCx), trifurcation (additional ramus intermedius), quadrifurcation (median/intermediate artery). b. Diagonal branches are discrete epicardial diagonals from LAD (septal perforators excluded). Diagonal mean 95% CIby normal approximation; proportion CIs by Wilson method. c. High take-off RCA = ostium >3 mm above sinutubular ridge; myocardial bridging recorded when a tunneled LAD segment was grossly evident. d. Percentages are based on n = 80; minor rounding differences may occur.

Short inference (Table 3): Classic LCA bifurcation predominated (~69%), while trifurcation with ramus occurred in about one-quarter and quadrifurcation was uncommon (~7–8%). The LAD most often had two diagonals (50%; mean 1.75), and rare but important variants—high take-off RCA, duplicated LAD, and myocardial bridging—appeared at single-digit frequencies, underscoring procedural implications for catheter choice, grafting strategy, and angiographic interpretation.

Termination Sites and Coronary Dominance

We quantified RCA/LCx termination sites and overall coronary dominance, and tested expected anatomical relationships between termination at the posterior interventricular region and dominance classification. (Table 4)

Table 4. Termination Sites of RCA and LCx with Coronary Dominance and Association Diagnostics (n = 80)

1. 2×2 table (LCx posterior septum vs dominance aggregated as Left/Balanced vs Right): counts [a,b;c,d] = [9,1; 0,70], Fisher’s exact two-sided p = 0.0007, confirming that LCx reaching the posterior septum strongly associates with non-right dominance.
   2×2 table (RCA posterior sulcus vs Right vs non-Right dominance): counts [a,b;c,d] = [12,0; 59,9], Fisher’s exact two-sided p = 0.0028, indicating RCA extension to posterior sulcus is associated with right dominance.
   c. Crux = intersection of AV and posterior interventricular grooves. Dominance was defined by the artery giving rise to the posterior descending artery (PDA).
   d. Percentages are based on n = 80; 95% CIs are Wilson intervals for proportions.

RCA most commonly terminated between the crux and obtuse margin (57.5%), while LCx did so in 73.8%. Dominance was overwhelmingly right-sided (88.8%). As expected, LCx to the posterior septumclustered with non-right dominance (Fisher’s p = 0.0007), and RCA to the posterior sulcus clustered with right dominance (p = 0.0028), supporting internal consistency between termination anatomy and dominance definitions.

Summary of Quantitative and Variant Findings

Consolidated overview of vessel morphometrics (lengths/diameters) and high-yield variants/dominance that influence angiography, CABG planning, and stent sizing. (Table 5)

Table 5.Summary of Quantitative Measurements and Key Variant Features (n = 80)

1. Lengths measured along anatomic course (RCA from ostium to termination; LCA trunk from ostium to first branch; LAD/LCx from bifurcation; PDA in posterior IV sulcus). Diameters measured proximally (ostium/just distal).
   95% CI of mean = mean ± 1.96 × (SD/√n); CV = SD/mean × 100%.
   c. Proportion 95% CIs are Wilson intervals; percentages computed from n = 80.
   d. High take-off RCA defined relative to the sinutubular ridge; accessory ostia most commonly conus or sinoatrial nodal openings.

The morphometric profile shows a length hierarchy (RCA > LAD > LCx > PDA) and diameter hierarchy (LCA > RCA > LAD > LCx) with substantial variability in the left main length (CV ≈ 51%). Variants of procedural relevance occur at low-to-moderate frequencies—notably multiple RCA ostia (27.5%), accessory conus/SA ostia (13.7%), and high take-off RCA (6.3%)—while duplicated LAD and myocardial bridgingare uncommon. The dominance pattern is overwhelmingly right-sided (88.8%), reinforcing consistency across the dataset and implications for PDA supply and graft/guide strategy.

Our 80-heart anatomical series offers an integrated picture of coronary origins, morphometry, branching architecture, terminations, and dominance with practical implications for imaging and intervention. The pattern is internally consistent: a uniform RCA origin from the anterior aortic sinus; LCA origin almost always from the left posterior sinus (2.5% ectopy); a predominantly below-ridge ostial position on both sides; LCA bifurcation as the modal left-main pattern (≈69%) with non-trivial trifurcation (~24%); and an overwhelmingly right-dominant circulation (~89%). Quantitatively, the RCA and LAD are the longest conduits, while the left main trunk is frequently short and highly variable (CV ≈51%). Variants such as multiple RCA ostia (27.5%), accessory conus/SA ostia (13.7%), high take-off RCA (6.3%), duplicated LAD (3.8%), and myocardial bridging (7.5%) occurred at low–moderate frequencies[11]. The strong tendency for both ostia to lie below the sinutubular ridge (RCA 88.7%, LCA 83.7%) explains why standard Judkins catheters seat predictably in most cases and why high take-off RCA can frustrate selective engagement. The 27.5% rate of multiple RCA ostia and 13.7% accessory conal/SA openings warn of contrast reflux and misregistration during aortography if small accessory ostia are not opacified. When pre-procedural CT is available, flagging above-ridgeor high take-off anatomy can avert prolonged fluoroscopy and contrast load[12,13].A short, variable left main (mean 5.3 mm; 2–14 mm range) has two practical consequences. First, ostial/proximal LM stenting requires precise landing to avoid geographic miss into the sinus or undue encroachment on LAD/LCx. Second, guide size and shape (back-up vs standard curves) may need adjustment to avoid trauma at a short LM take-off—particularly in calcified roots[14,15]Branching architecture and revascularization planning.

The ≈24% prevalence of trifurcation (ramus intermedius) and 7–8% quadrifurcation create true multi-ostial carinas at the LM. Even in the absence of atherosclerosis, these patterns complicate bifurcation/trifurcation stenting (branch protection, final kissing/rewiring strategy) and influence bypass plans (e.g., whether to graft a sizable ramus). The LAD diagonal distribution (most commonly two; mean ≈1.75) helps anticipate competitive flow and anastomotic targets[16,17].Two internal checks support an anatomically coherent dataset: (i) LCx reaching the posterior septum clustered with non-right dominance (Fisher’s p=0.0007), and (ii) RCA reaching the posterior sulcus clustered with right dominance(p=0.0028). This reinforces the textbook notion that PDA supply determines dominance and validates our gross mapping against functional perfusion territories[18,19].

Though infrequent, high take-off RCA, duplicated LAD, and myocardial bridging are worth explicit reporting. High take-off influences catheter choice and aortotomy orientation; duplicated LAD can alter graft planning and lesion localization; myocardial bridging, typically mid-LAD, may protect against plaque but can be ischemia-provoking in tachycardia—facts that change stress-test interpretation and surgical myotomy decisions in select patients[20].

Strengths and limitations

Strengths include (i) a comprehensive morphological frame (origins → morphometry → branching → dominance → terminations) examined within one cohort, (ii) a priori diagnostics (CIs; paired/association tests) to check internal consistency, and (iii) explicit reporting of low-frequency variants that are easy to miss in smaller series.

Limitations are typical of cadaveric work: (i) formalin fixation may subtly shrink diameters; (ii) absence of body-size indexing (BSA/heart weight) limits normalization of lengths/diameters; (iii) single-center sampling risks regional or procurement bias; (iv) lack of in-vivo correlation (angiography/CT) precludes direct translation of absolute cut-offs; and (v) variant frequencies—especially those <10%—carry wide CIs, so replication is warranted.

Implications and future directions

These data argue for routine structured coronary mapping in anatomical teaching and in surgical planning notes, with explicit mention of (a) ostial height, (b) left-main length, (c) LM branching type (bi/tri/quad-furcation), (d) diagonal count, and (e) dominance and posterior termination. Future work should (i) index morphometry to BSA, (ii) pair cadaveric findings with CT angiography in matched populations, and (iii) explore automated measurement pipelines to reduce observer variability

In 80 formalin-fixed hearts, coronary anatomy followed a coherent pattern: uniform RCA origin, near-uniform LCA origin, ostia typically below the sinutubular ridge, LCA bifurcation predominance, and right-sided dominance. The left main trunk is frequently short and variable, and clinically salient variants—notably multiple RCA ostia, accessory conal/SA ostia, and high take-off RCA—are common enough to merit active surveillance during imaging and intervention. Internal association tests between posterior terminations and dominance confirm anatomical consistency. Collectively, these findings refine expectations for catheter selection, stent landing, and graft targeting, and provide a pragmatic anatomic baseline for procedure planning and teaching.

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