The PAC medical abbreviation most often means premature atrial contraction, an extra heartbeat that starts early in one of the upper chambers of the heart. Cardiology notes, EKG reports and telemetry strips usually write it in the plural, PACs, because these beats tend to come and go.
PAC has a few other uses. In intensive care it can mean pulmonary artery catheter, in hormone testing it can mean plasma aldosterone concentration, and in radiology PACS is the picture archiving and communication system that stores scans. This page sorts out each meaning, decodes a telemetry line and compares PACs with similar rhythm terms.
At a glance
Stands for
Premature atrial contraction (cardiology, most common)Other meanings
Pulmonary artery catheter; plasma aldosterone concentration; PACS imaging archiveAlso called
Premature atrial complex, atrial premature beat, APCWhere you see it
EKG reports, telemetry notes, Holter monitor results, nursing notesDo not confuse with
PVC (early beat from the lower chambers)Plural or forms
PACs, frequent PACs, PAC burden
What a premature atrial contraction is
Each regular beat is normally triggered by the sinus node, the heart's built in pacemaker tissue high in the right atrium. With a PAC, another spot in the atria fires first, so a beat arrives sooner than expected. It is usually followed by a short pause while the rhythm resets. People who notice them describe a skipped beat, a flutter or a thump in the chest, but many feel nothing at all.
PACs are very common and are found in most adults on long recordings. Triggers can include caffeine, alcohol, nicotine, stress, poor sleep and some medicines. In many people they need no treatment. Doctors pay closer attention when they are very frequent, cause symptoms, or appear with structural heart disease.
PAC medical abbreviation in EKG and telemetry notes
Telemetry nurses and cardiology fellows write PACs in short rhythm summaries. The surrounding words tell you how often they occurred and whether they mattered.
| Piece | Meaning |
|---|---|
| Tele | Continuous heart monitoring on the unit |
| NSR | Normal sinus rhythm as the main rhythm |
| occasional PACs | Scattered early atrial beats |
| no ectopy runs | No strings of extra beats in a row |
| asymptomatic | The patient did not feel them |
Holter report: "Frequent PACs, burden 4 percent, one 6 beat run of atrial tachycardia." Burden means the share of all beats that were PACs, and the short run is noted because it can be reviewed with the clinician.
PACs compared with PVCs and other rhythms
| Term | Where it starts | What it means |
|---|---|---|
| PAC | Upper chambers (atria) | Single early beat |
| PVC | Lower chambers (ventricles) | Single early beat, usually wide on EKG |
| SVT | Above the ventricles | Sustained fast rhythm |
| PAF | Atria | Atrial fibrillation that comes and goes |
On an EKG, a PAC usually shows an early, oddly shaped P wave followed by a normal looking narrow complex. A PVC skips the P wave and produces a wide complex. Frequent PACs are sometimes watched more closely because they can be linked with later atrial fibrillation in some people.
Pulmonary artery catheter in the ICU
In critical care and cardiac surgery notes, PAC can mean pulmonary artery catheter, a thin tube passed through a large vein, through the right heart chambers, and out into the pulmonary artery. It measures pressures inside the heart and lungs and helps estimate how well the heart is pumping. Many staff still call it a right heart catheter or use an older brand based nickname.
The giveaway is context: a note mentioning PA pressures, wedge pressure, cardiac output or an introducer sheath is talking about the catheter, not an early heartbeat.
PACS in radiology and PAC in hormone tests
When a clinician says "the images are in PACS," they mean the picture archiving and communication system, the computer system hospitals use to store and view x rays, CT scans and MRI studies. It has nothing to do with heart rhythm, even though the letters match the plural of PAC.
In endocrinology, PAC can mean plasma aldosterone concentration. It is measured together with renin to calculate the aldosterone to renin ratio, a screening test for primary aldosteronism, a cause of high blood pressure. These pages in the diagnosis abbreviations section cover related heart terms.
Questions about PACs worth raising
- How many PACs did the monitor record, and is that a lot?
- Could caffeine, alcohol, sleep or a medicine be playing a part?
- Do I need any further tests, such as an echocardiogram?
- Which symptoms should prompt a call or an urgent visit?
Extra heartbeats mean different things for different people. Whoever ordered your monitor or EKG can walk you through what the rhythm results show and whether anything should change.
Frequently asked questions
What does PAC mean on an EKG?
It means premature atrial contraction, an early beat starting in the upper chambers of the heart. Reports often list them as occasional or frequent PACs.
Are PACs dangerous?
In most healthy people, occasional PACs are considered harmless. They get more attention when they are very frequent, cause symptoms, or occur with other heart conditions, and that judgment belongs to the treating clinician.
What does PACS mean in a hospital?
PACS usually means the picture archiving and communication system that stores medical images. In a cardiology note, PACs with a lowercase s just counts more than one premature atrial contraction.
What is the difference between a PAC and a PVC?
A PAC starts in the atria, the upper chambers, while a PVC starts in the ventricles, the lower chambers. They look different on an EKG and are assessed in slightly different ways.
What does PAC mean in nursing notes?
As a nursing abbreviation on a cardiac or telemetry unit, PAC nearly always means premature atrial contraction. In an ICU note about pressures, it can mean pulmonary artery catheter.
Is PAC a medical acronym for a doctor or a credential?
When a doctor writes PAC in a heart note, it means an early atrial beat, not a person. The physician assistant credential is written PA-C with a hyphen and has its own page. PACS, read aloud as a word, is the medical acronym for the imaging storage system.