What Is the Posterior Interventricular Artery?

The posterior interventricular artery, more commonly called the posterior descending artery (PDA), is the vessel that runs along the bottom groove of the heart between the two ventricles and feeds blood to the inferior wall of the left ventricle and the lower portion of the interventricular septum. In roughly four out of five people, this artery branches off from the right coronary artery, but the minority pattern where it arises from the left side turns out to carry measurably different clinical risks. Understanding this single vessel clarifies a surprising amount about heart attacks, heart block, and even which patients fare worse after an acute coronary event.

Where the Artery Comes From and What That Means

Cardiologists use the term “coronary dominance” to describe which parent artery gives rise to the PDA. When the right coronary artery (RCA) supplies the PDA, the heart is called right-dominant. When the left circumflex artery (LCx) supplies it, the heart is left-dominant. And when both sides contribute, the term is codominant. A large autopsy study found right dominance in about 81% of hearts, left dominance in roughly 9%, and codominance in close to 10%.¹ That same study noted that the proportion of left-dominant and codominant hearts decreased with age, suggesting that dominance pattern may influence long-term cardiovascular outcomes or that selection effects thin out certain patterns over a lifetime.

Dominance is not just an anatomical curiosity. Because the PDA feeds the inferior septum, the inferior left ventricular wall, and often the atrioventricular (AV) node, knowing which parent vessel gives rise to it immediately tells a clinician how much territory is at risk when that parent vessel develops a blockage. In a right-dominant heart, an RCA occlusion can knock out the PDA’s territory all at once. In a left-dominant heart, a circumflex occlusion does the same, but with added consequences because the left coronary system is already responsible for the anterior and lateral walls. The PDA’s origin, in other words, determines how concentrated or spread out the heart’s vulnerability is.

The Territory the PDA Supplies

The PDA travels in the posterior interventricular groove, the shallow furrow on the underside of the heart separating the right and left ventricles. Along its course it sends small perforating (septal) branches into the lower third of the interventricular septum. These septal branches are critical because the septum houses the heart’s electrical wiring, including the bundle of His and its branches. The PDA also gives off small branches to the adjacent inferior walls of both ventricles, though its main nutritional obligation is to the left ventricle’s inferior surface.

One clinically important structure that often depends on the PDA’s blood supply is the posteromedial papillary muscle. This muscle anchors the mitral valve’s leaflets and keeps them from flipping backward when the left ventricle contracts. Unlike the anterolateral papillary muscle, which receives blood from two separate coronary branches, the posteromedial papillary muscle typically has a single arterial supply, frequently the PDA or another branch of whatever artery is dominant.² That single-source blood supply makes it far more vulnerable to ischemic damage than its counterpart on the other side of the valve.

When the PDA Is Blocked

A heart attack involving the PDA’s territory presents as an inferior myocardial infarction. On an electrocardiogram, the classic signs show up in the leads that look at the bottom of the heart. The consequences extend beyond muscle damage, though, because the PDA’s septal branches may feed the AV node. Loss of that blood supply can produce heart block, ranging from mild first-degree block (a slowed electrical signal) to complete third-degree block where the atria and ventricles beat independently. In most right-dominant hearts, the AV nodal artery itself arises near where the RCA gives off the PDA, so a proximal RCA occlusion can simultaneously knock out the PDA and the AV nodal supply.

Two structural complications of inferior heart attacks trace directly to PDA territory. The first is rupture of the posteromedial papillary muscle. Because that muscle’s blood supply is often a single branch from the PDA or the dominant artery, an infarct in this zone can cause the muscle to partially or fully tear, resulting in sudden, severe mitral valve leakage. This is a surgical emergency. The second complication is a posterior ventricular septal defect, where the infarcted septum breaks down and a hole forms between the ventricles. Surgical repair of posterior septal defects often involves an incision along the PDA itself to access the damaged tissue.³ In some cases the posteromedial papillary muscle survives the infarct, but its margin of safety is thin.

Does Coronary Dominance Affect Prognosis?

The short answer is yes, and in ways that are not entirely intuitive. You might expect that left-dominant hearts, where the left coronary system shoulders more responsibility, would be fine as long as the left side stays healthy. But multiple studies have found the opposite pattern: left dominance is associated with worse outcomes after acute coronary events. A large study of patients with acute coronary syndromes found that those with left dominance had significantly higher long-term mortality, with an adjusted hazard ratio of about 1.13 compared to right-dominant patients.⁴ A review in the Journal of the American Heart Association confirmed this trend, noting that left dominance has been linked to poorer outcomes across ischemic heart disease, conduction disorders, and valvular disease.⁵

The reasoning is straightforward once you think about it. In a left-dominant heart, the left coronary system supplies the anterior wall, the lateral wall, and the inferior wall through the PDA, essentially the entire left ventricle. A single lesion in the left main or proximal left circumflex artery puts an enormous amount of heart muscle at risk. In right-dominant hearts, the workload is split more evenly between the right and left coronary systems, so no single blockage can jeopardize as large a territory.

The picture flips somewhat for inferior infarctions specifically. A case-control study found that right dominance was associated with roughly twice the odds of acute inferior myocardial infarction compared to non-right-dominant patterns, after adjusting for conventional risk factors like smoking, diabetes, and high blood pressure.⁶ This makes anatomical sense: in a right-dominant heart, the RCA is a larger vessel carrying more flow, and its occlusion wipes out the PDA territory entirely. So the overall mortality disadvantage falls on left-dominant patients, while the specific risk of inferior infarction is higher in right-dominant hearts. Dominance acts as a kind of geographic risk modifier rather than a simple good-or-bad label.

Anatomical Variations and Rare Anomalies

The standard textbook picture of the PDA arising neatly from the RCA or the LCx does not capture the full range of human anatomy. A handful of unusual origin patterns have been documented. One report described the PDA arising from a vascular ring, an abnormal communication between the right coronary artery and the left circumflex artery within the groove between the atria and ventricles. The PDA branched off from this ring and then followed its normal path along the inferior septum.⁷

Other documented oddities include the PDA originating from an obtuse marginal branch, from a septal perforator artery, or even as a direct continuation of the left anterior descending artery (LAD) wrapping all the way around the apex of the heart. This last variant is sometimes called a “superdominant” or “hyperdominant” LAD.⁸ Double PDAs, where two parallel vessels share the inferior groove, have also been reported in a small percentage of angiograms.⁹

Most of these anomalies are discovered incidentally during cardiac catheterization and do not cause symptoms on their own. Their significance is mostly surgical and interventional: a cardiologist planning a stent placement or a surgeon grafting a bypass needs to know exactly where the PDA originates and what it feeds. Mistaking a wraparound LAD for a separate PDA, or missing a vascular ring, can change the operative plan substantially.

Intervening on PDA Disease

When plaque builds up in the PDA or at the junction where the PDA branches off its parent vessel, the standard options are angioplasty with stent placement or coronary bypass surgery. The bifurcation where the RCA gives off the PDA can be a technically challenging spot for stenting, because bifurcation lesions in general carry higher rates of restenosis and procedural complication than straight-segment disease. Various techniques have been developed to manage bifurcation stenting across the coronary tree, and the RCA-PDA junction is one of several sites where these techniques are applied.¹⁰

For bypass surgery, the PDA is a common target vessel. Surgeons typically use either a segment of saphenous vein from the leg or, less often, a smaller arterial graft to create a new route around the blockage. The choice depends on how many other vessels need bypassing, the patient’s age, and the quality of the native artery beyond the obstruction. Because the PDA runs along the underside of the heart, the surgeon must physically lift and rotate the heart during the operation to reach it, a maneuver that can briefly compromise blood pressure and requires careful hemodynamic management.

Imaging the PDA Without a Catheter

Coronary angiography, where a catheter is threaded into the coronary arteries and contrast dye is injected, remains the gold standard for visualizing the PDA. But less invasive options have improved. Coronary CT angiography can now identify the PDA’s origin, course, and major branch points with good spatial resolution. For assessing whether blood flow through the PDA is actually adequate, though, the picture gets murkier.

Transthoracic Doppler echocardiography can measure flow velocities in coronary arteries through the chest wall. It has been used successfully to measure coronary flow reserve in the LAD for years, and researchers have extended the technique to the PDA. Early work demonstrated that baseline PDA flow could be detected in about three-quarters of subjects, but measuring flow reserve, which requires comparing resting flow to flow during a stress agent like adenosine, was only feasible in roughly half due to adenosine-induced hyperventilation interfering with the signal.¹¹ Later studies explored additional imaging windows and probe positions to improve the detection rate.¹²

The technique has even been applied in pediatric populations, where catheter-based angiography carries higher relative risk. One study evaluated coronary flow velocity reserve in the PDA of children with elevated right ventricular pressure, using adenosine as the stress agent at a slightly different dose than in adults.¹³ This kind of non-invasive testing has obvious appeal in children but remains technically demanding and is not yet routine in most echocardiography labs.

How the PDA Forms Before Birth

The coronary arteries do not simply sprout from the aorta and grow outward. During embryonic development, vascular networks form in the grooves of the developing heart, and these networks are later connected to the aorta by ingrowth of the coronary stems. Research on human embryos at early developmental stages described the formation of subepicardial vascular networks along the atrioventricular and interventricular grooves, with distinct right-posterior and left-anterior networks emerging as precursors to the adult coronary branches.¹⁴ The right-posterior network is the forerunner of the PDA and its related branches.

This developmental pattern helps explain why coronary anomalies, including unusual PDA origins, exist at all. The final anatomy depends on which parts of these early networks persist, enlarge, and connect to the main coronary stems, and which parts regress. Small variations in that remodeling process can produce a PDA that comes from an unexpected source while still following a normal branching pattern once it reaches the inferior groove. The vascular ring anomaly described earlier, where the RCA and LCx communicate abnormally and the PDA branches off the ring, likely represents a segment of the primitive atrioventricular groove network that persisted instead of regressing.

Why the PDA Gets Less Attention Than the LAD

In popular awareness and even in some medical training, the left anterior descending artery dominates the conversation. It has been called “the widow-maker” because blockages there can cause massive anterior heart attacks, and it is the most commonly diseased coronary vessel. The PDA, by contrast, tends to be discussed mainly as a footnote to coronary dominance. But the clinical stakes of PDA disease are not trivial. Inferior infarctions account for a substantial share of all heart attacks, and their complications, including heart block, papillary muscle rupture, and posterior septal defects, can be lethal.

Part of the PDA’s lower profile comes from anatomy itself. The LAD is accessible on the anterior surface of the heart and is easy to image with echocardiography and CT. The PDA sits on the inferior surface, tucked against the diaphragm, making it harder to visualize non-invasively and harder to reach surgically. The feasibility gap in Doppler imaging between the two vessels illustrates this well: flow in the LAD can be detected in the vast majority of patients, while PDA detection rates are considerably lower. That imaging asymmetry trickles into clinical research, where LAD-focused studies far outnumber PDA-focused ones, creating a self-reinforcing cycle in which the vessel that is harder to study remains less studied.

For patients, the practical implication is simple. If your angiogram or CT report mentions the PDA, coronary dominance, or inferior wall ischemia, those terms are pointing at this artery and the territory it serves. Knowing whether you have right or left dominance, something any catheterization report will state, gives both you and your cardiologist a clearer picture of which parts of your heart are most at risk and how a blockage in one vessel might cascade into complications that go well beyond a single damaged patch of muscle.