The posterior interventricular sulcus is a shallow groove on the underside of the heart that marks the boundary between the left and right ventricles along their back-facing (diaphragmatic) surface. It runs from a landmark called the crux cordis, where several of the heart’s grooves converge near the top, down toward the pointed tip (apex) of the heart. Inside this groove sit the posterior descending artery, the middle cardiac vein, and a variable amount of fat, all of which make the sulcus far more than a simple surface marking. Its clinical importance shows up most clearly in inferior heart attacks, where the blood supply running through the groove can be suddenly cut off.
Where It Sits on the Heart
The heart has two interventricular sulci, one on each major surface. The anterior interventricular sulcus runs along the front of the heart, visible when you look at the sternum-facing side. The posterior interventricular sulcus runs along the underside, the surface that rests against the diaphragm. Together, the two grooves trace the dividing line between the ventricles almost completely around the organ, meeting near the apex in a small notch.
The posterior sulcus begins at the crux cordis, a crossroads where the posterior interventricular groove meets the atrioventricular groove (the horizontal groove separating the atria from the ventricles on the back of the heart). From the crux, it extends inferiorly toward the apex. A CT angiographic study of 356 patients divided the sulcus into three segments following the American Heart Association classification: a basal segment nearest the crux, a mid-ventricular segment, and an apical segment closest to the tip of the heart.1PubMed. Arterial supply of the posterior interventricular sulcus: a CT coronary angiographic study That segmental breakdown matters clinically because each segment can be fed by a different coronary artery branch, and a blockage in one area may leave the other segments unaffected.
The Naming Debate
If you have read conflicting labels for this structure, you are not imagining it. Older anatomy textbooks almost universally call it the “posterior” interventricular sulcus, and many clinicians still use that term. But a push for what is known as attitudinally correct nomenclature points out that the so-called posterior surface of the heart does not actually face backward. In a living person standing upright, this surface rests on the diaphragm and faces downward, making “inferior” a more accurate directional label.2PubMed Central. Attitudinally correct nomenclature
The same logic applies to the “posterior descending artery,” which many newer references call the “inferior interventricular artery” or simply the posterior interventricular artery. In clinical cardiology, though, the old labels persist. Cardiologists discussing coronary dominance still routinely say “PDA” for the posterior descending artery. The takeaway is that “posterior interventricular sulcus” and “inferior interventricular sulcus” describe the same groove. If you encounter both in different textbooks, the anatomy has not changed; only the directional convention has.
What Runs Through the Groove
Three main structures sit inside the posterior interventricular sulcus, cushioned by a strip of epicardial fat.
- Posterior descending artery: This is the primary arterial conduit in the groove. It supplies blood to the inferior portion of the interventricular septum and parts of both ventricular walls. Where it originates from determines what cardiologists call “coronary dominance,” a concept with real consequences during heart attacks.
- Middle cardiac vein: Running alongside the artery, this vein collects deoxygenated blood from the inferior walls of both ventricles and drains it into the coronary sinus, a large vein on the back of the heart that empties into the right atrium.
- Epicardial fat: A layer of adipose tissue fills the remaining space in the groove. This fat is metabolically active and, in some research contexts, its volume has been studied as a marker of cardiovascular risk, though that work relates more to overall epicardial fat deposits than to the sulcus specifically.
The middle cardiac vein, while less discussed than the artery, has practical significance for electrophysiologists. When mapping the source of abnormal heart rhythms that originate in the coronary venous system, a study of patients undergoing catheter ablation found that about 7% of those ventricular arrhythmias arose from the middle cardiac vein, compared with roughly half from the great cardiac vein and 40% from the anterior interventricular vein.3Heart Rhythm. Ventricular arrhythmias from the coronary venous system: Prevalence, mapping, and ablation That makes the middle cardiac vein a less common site for arrhythmias, but one that electrophysiologists still need to explore when the usual locations come up empty.
Coronary Dominance and Why It Matters Here
The single most clinically important feature of the posterior interventricular sulcus is which coronary artery sends a branch to supply it. In most people, the posterior descending artery arises from the right coronary artery, a pattern called right dominance. In a smaller fraction, it comes from the left circumflex artery, called left dominance. These two patterns change which artery, when blocked, will cause an inferior heart attack.
A CT angiographic study of 356 patients found right dominance in about 87%, left dominance in roughly 10%, and a balanced pattern (both arteries contributing equally) in about 3%.4PubMed. Arterial supply of the posterior interventricular sulcus: a CT coronary angiographic study A separate study using multi-detector CT angiography on 50 patients found the posterior descending artery originating from the right coronary artery in 78% of cases and from the left circumflex in 22%.5Academia Anatomica International. PDA (Posterior Descending Artery) Coronary Dominance-A MDCT Coronary Angiographic Analysis of Anatomic Variations and Clinical Importance The difference in percentages between these studies reflects normal variation across populations and sample sizes, but both confirm the same broad picture: right dominance is by far the most common arrangement, and left dominance is the minority pattern.
For patients, dominance matters because it determines vulnerability. In a right-dominant heart, an acute blockage of the right coronary artery can cut off blood flow to the inferior wall of the left ventricle, the inferior septum, and often the right ventricle. In a left-dominant heart, the same territory is at risk when the left circumflex artery is blocked instead. Knowing a patient’s dominance pattern before or during an emergency procedure helps cardiologists locate the culprit vessel more quickly.
Surprising Variety in Blood Supply Patterns
One of the underappreciated details about the posterior interventricular sulcus is just how many different arterial supply patterns exist. The CT angiographic study that divided the sulcus into three segments found 25 distinct irrigation patterns across its 356 patients.6PubMed. Arterial supply of the posterior interventricular sulcus: a CT coronary angiographic study That is a striking number. Most people assume the posterior descending artery simply runs the full length of the groove, but the reality is much more patchwork.
The most common pattern, seen in about 31% of patients, involved a single right coronary artery branch feeding the basal and mid-ventricular segments, while the left anterior descending artery wrapped around the apex of the heart and entered the sulcus from below to supply the apical segment.7PubMed. Arterial supply of the posterior interventricular sulcus: a CT coronary angiographic study In other words, even in the single most common arrangement, two different arteries share the groove. Individual segments were perfused by a single artery in about 81% of cases, while the remaining 19% had segments receiving blood from more than one source.
This variability explains something cardiologists see regularly on angiograms: the posterior descending artery does not always reach the apex. In the separate MDCT study, the artery terminated in the upper quarter of the groove in 36% of cases, in the upper half in 38%, in the upper three-quarters in 20%, and reached the apex in only 2%.8Academia Anatomica International. PDA (Posterior Descending Artery) Coronary Dominance-A MDCT Coronary Angiographic Analysis of Anatomic Variations and Clinical Importance So in the majority of people, the posterior descending artery covers only part of the sulcus, and additional branches from other arteries fill in the rest. The apex, in particular, often depends on the left anterior descending artery wrapping around from the front of the heart.
Clinical Significance in Inferior Heart Attacks
The posterior interventricular sulcus is ground zero for inferior myocardial infarctions, sometimes still called posterior infarctions in older clinical language. When the artery supplying this groove is blocked by a clot, the muscle on both sides of the sulcus loses its blood supply. Symptoms typically include chest pain, nausea, and sometimes a dangerous drop in heart rate because the artery supplying the groove also often feeds the heart’s electrical conduction system near the crux.
Rare anatomic variants can complicate emergency diagnosis. In one documented case, a patient presenting with an acute inferior wall heart attack and hemodynamic instability underwent emergency coronary angiography. The angiogram appeared to show a patent (open) right coronary artery, suggesting the infarct-related vessel was not blocked. In reality, the vessel that looked like the right coronary artery was actually a posterior interventricular branch with an unusually early origin from the right coronary artery. The true right coronary artery, which was completely occluded by a clot, was a separate vessel that was not initially recognized.9Wiley Online Library. 10PubMed Central. Transatrial Approach for the Repair of the Posterior Post-Infarct Ventricular Septal Rupture The difficulty is partly anatomical: the posterior septum is harder to reach and harder to patch securely, and the surrounding tissue is often too damaged by the infarction to hold sutures well.
Arrhythmias and Electrophysiology Procedures
Beyond its role in coronary artery disease, the posterior interventricular sulcus is relevant to cardiac electrophysiology. The middle cardiac vein running through the groove can occasionally be the source of abnormal electrical activity that triggers ventricular arrhythmias. When electrophysiologists map these arrhythmias using catheters threaded through the coronary venous system, they occasionally find the origin deep in or near the middle cardiac vein.
These cases are relatively rare compared to arrhythmias originating from the great cardiac vein or the anterior interventricular vein, but they present unique challenges. The middle cardiac vein is narrower, and maneuvering an ablation catheter into it requires more care. The proximity of the posterior descending artery also creates a risk of thermal injury to the vessel during ablation. Electrophysiologists treating arrhythmias from this location typically use imaging to map the precise relationship between the vein, the artery, and the site of abnormal electrical activation before delivering energy.
Why the Sulcus Does Not Look the Same in Everyone
Anatomical variability is the rule, not the exception, when it comes to the posterior interventricular sulcus and its contents. Beyond the 25 arterial supply patterns already discussed, the depth and prominence of the groove itself differ from person to person. In some hearts, the sulcus is a well-defined channel easily visible on the epicardial surface. In others, particularly in hearts with significant epicardial fat deposits, the groove is nearly invisible under a thick layer of adipose tissue and can only be identified by the course of the vessels within it.
The position where the left anterior descending artery wraps around the apex to enter the posterior sulcus is another source of variation. In some individuals, the left anterior descending artery terminates well before reaching the back of the heart, leaving the apical segment of the sulcus dependent on small branches from the posterior descending artery or from septal perforators. In others, the left anterior descending artery travels a considerable distance into the posterior groove, supplying a large territory that in a textbook diagram would “belong” to the posterior descending artery. This overlap means that the functional boundary between the territories of the two main interventricular arteries is not fixed; it shifts depending on individual anatomy.
For surgeons and interventional cardiologists, this variability is a practical concern, not an academic curiosity. Bypass grafting strategies, stent placement decisions, and even the interpretation of stress tests all depend on understanding which artery supplies which part of the sulcus in a given patient. Preoperative CT angiography has become a valuable tool for mapping these patterns before any procedure, precisely because assuming a textbook arrangement can lead to missed lesions or misdirected interventions.
Epicardial Fat in the Groove
The strip of fat filling the posterior interventricular sulcus is part of the larger epicardial fat depot that surrounds the heart. Unlike the subcutaneous fat most people think of, epicardial fat sits directly on the heart muscle with no fascial barrier separating the two. This intimate contact means that inflammatory signals from epicardial fat can directly affect the underlying myocardium and coronary vessels.
In the sulcus specifically, the fat cushions the posterior descending artery and the middle cardiac vein, protecting them from mechanical stress as the heart contracts. But excessive epicardial fat, which tends to accumulate with obesity and metabolic syndrome, can compress these structures and may contribute to local inflammation around the coronary artery. Cardiac imaging studies increasingly measure epicardial fat volume as part of cardiovascular risk assessment, though the clinical guidelines on what to do with that measurement are still evolving.
For cardiac surgeons, the fat in the sulcus is something they encounter directly. When performing coronary bypass surgery, the surgeon must sometimes dissect through epicardial fat to identify the posterior descending artery or to locate an appropriate site for a graft anastomosis. In hearts with abundant fat, finding the target vessel can be genuinely difficult, and the middle cardiac vein, which runs close to the artery, can be mistaken for it or inadvertently injured. Awareness of the groove’s anatomy and its fat-filled character helps surgeons navigate this territory more safely.