When you’re managing a serious mental health condition like schizophrenia, the last thing you want to worry about is your heart. But for many people taking antipsychotics, that’s exactly what doctors are asking them to do: monitor their heart rhythm. Why? Because some of these life-saving psychiatric drugs can stretch out the QT interval on an ECG - a change that, in rare but dangerous cases, can trigger a fatal heart rhythm called torsade de pointes.

What Exactly Is QT Prolongation?

The QT interval on an electrocardiogram (ECG) measures how long it takes your heart’s ventricles to recharge between beats. If that interval gets too long - known as QT prolongation - your heart can slip into an irregular, chaotic rhythm. The corrected QT interval, or QTc, adjusts for heart rate. A QTc over 500 milliseconds is considered clinically dangerous. If it jumps more than 60 ms from your baseline, or hits 550 ms or higher, it’s a red flag that needs immediate action.

This isn’t theoretical. In the UK, heart rhythm specialists see this regularly. A 2023 study of 1,200 psychiatric inpatients found nearly 1 in 5 developed a QTc over 500 ms while on antipsychotics. Most of those cases involved taking more than one drug that affects the heart. That’s the real danger: combinations.

Which Antipsychotics Carry the Highest Risk?

Not all antipsychotics are created equal when it comes to heart risk. The differences are stark.

Thioridazine - once a common treatment - was pulled from the U.S. market in 2005 because it prolonged the QT interval by up to 35 milliseconds. It’s a classic example of a drug that saved lives from psychosis but cost lives through cardiac arrest.

Haloperidol, still widely used, especially in hospitals, adds about 4-6 ms to the QTc. That might sound small, but in someone with low potassium, kidney problems, or on other heart-affecting meds, that tiny push can be enough to tip them into danger.

Ziprasidone has a mixed reputation. Pharmacovigilance data shows it’s linked to a reporting odds ratio of 4.9 for QT prolongation - meaning it’s flagged more often than most. But a major 2023 ICU study found no significant QT increase in critically ill patients compared to placebo. Why the contradiction? Context matters. In a healthy person, ziprasidone may be fine. In someone on diuretics, with low magnesium, and already on a beta-blocker? That’s a recipe for trouble.

At the bottom of the risk ladder? Lurasidone. Studies show it barely moves the needle - just 1-2 ms on average. It’s now a go-to option for patients with heart conditions or those on multiple cardiac medications.

The CredibleMeds classification breaks it down clearly:

• High risk: Thioridazine, haloperidol, ziprasidone
• Moderate risk: Quetiapine, risperidone, iloperidone
• Low risk: Lurasidone, aripiprazole, brexpiprazole, paliperidone

Cardiac Medications That Make Things Worse

Antipsychotics don’t act alone. Many heart drugs also prolong the QT interval - and when they’re taken together, the effect multiplies.

Common offenders include:

• Antiarrhythmics like amiodarone and sotalol
• Antibiotics like moxifloxacin and erythromycin
• Antifungals like fluconazole and ketoconazole
• Some antidepressants, especially citalopram and escitalopram
• Diuretics that cause low potassium or magnesium

A 2023 study found that 68% of patients with dangerous QT prolongation were on two or more QT-prolonging drugs. That’s not an accident. It’s a prescribing gap.

Doctors sometimes focus so hard on treating psychosis or depression that they forget to check the heart drug list. A patient on risperidone for schizophrenia, citalopram for anxiety, and furosemide for fluid retention? That’s a triple threat. And if they’re over 65, female, or have kidney disease? The risk spikes again.

Who’s Most at Risk?

Some people are just more vulnerable. Risk factors aren’t just about the drugs - they’re about the person.

• Age over 65: Odds of QT prolongation increase by 2.3 times.
• Female sex: Women have a 1.7 times higher risk than men.
• Low potassium (hypokalemia): Found in 28% of cases with QTc > 500 ms.
• Low magnesium: Under 1.8 mg/dL significantly increases vulnerability.
• Heart disease: History of heart failure, prior arrhythmias, or prolonged QTc baseline.
• Genetic factors: Some people carry silent mutations that make them extra-sensitive to QT-prolonging drugs.

It’s not enough to just look at the drug. You have to look at the whole picture. A 72-year-old woman on haloperidol for delirium, with mild kidney impairment and a potassium level of 3.4? She’s not just at risk - she’s in a danger zone.

What Should Doctors Do?

The British Heart Rhythm Society and other guidelines give clear steps:

1. Get a baseline ECG before starting any high- or moderate-risk antipsychotic.
2. Repeat the ECG one week after reaching a steady dose. That’s when levels peak and effects are clearest.
3. Check electrolytes. Potassium should be above 4.0 mmol/L. Magnesium above 1.8 mg/dL.
4. Review all other medications. Use tools like CredibleMeds or a drug interaction checker. If you’re adding a new drug, ask: does this add to the QT burden?
5. Monitor high-risk patients closely. Inpatients on haloperidol or ziprasidone should have continuous cardiac monitoring for the first 24-48 hours.
6. Consider switching. If QTc rises above 500 ms, or increases by more than 60 ms from baseline, switch to a lower-risk agent like lurasidone or aripiprazole.

A 2021 survey showed that 73% of psychiatrists order baseline ECGs for high-risk antipsychotics - but only 32% do so for moderate-risk ones. That’s a problem. Many moderate-risk drugs, like quetiapine, can still cause dangerous prolongation in vulnerable patients.

What About the Benefits?

It’s easy to focus on the risks - and yes, they’re real. But ignoring antipsychotics is far more dangerous.

People with schizophrenia have a 5% lifetime risk of suicide. They’re 12% more likely to die from accidents. Studies show that those who take antipsychotics have 40% lower overall mortality than those who don’t. The risk isn’t in taking the drug - it’s in not taking it when you need it.

The mortality curve is U-shaped: people on no medication and those on the highest doses have the worst outcomes. The sweet spot? Low to medium doses, carefully monitored.

As one expert put it: “Assume all antipsychotics carry an increased risk of sudden cardiac death - but also assume that not treating psychosis carries a greater risk.”

What Can Patients Do?

You don’t need to be a doctor to protect yourself.

• Know your meds. Ask your pharmacist or doctor: “Does this drug affect my heart rhythm?”
• Keep track of your ECG results. Ask for a copy. Know your QTc number.
• Report symptoms: dizziness, fainting, palpitations, or sudden shortness of breath. Don’t wait.
• Don’t skip blood tests. Potassium and magnesium matter. If you’re on diuretics, ask if you need supplements.
• Bring all your meds - including over-the-counter and herbal - to every appointment.

Many people don’t realize that common cold medicines, antacids, or even some herbal supplements can affect QT. St. John’s Wort, for example, can interfere with metabolism and raise levels of antipsychotics in the blood.

The Future Is Monitoring - Not Avoidance

The FDA now requires all new antipsychotics to pass a “thorough QT study” before approval. That’s good. It means safer drugs are coming. Lurasidone’s sales grew 14% in 2022 as doctors shifted toward lower-risk options. Haloperidol sales dropped.

By 2026, ECG monitoring for antipsychotic users is expected to rise by 22%. Telemedicine ECGs are making it easier to check heart rhythms without hospital visits. Integrated care models - where psychiatrists and cardiologists talk - are becoming standard.

This isn’t about fear. It’s about smart management. Antipsychotics are essential. But they’re not harmless. With the right checks - baseline ECGs, electrolyte balance, drug reviews, and patient awareness - the risks can be managed without giving up the benefits.

The goal isn’t to stop treatment. It’s to make it safer. Because for many, the alternative - untreated psychosis - is far worse than a monitored heart.