Calcium channel blockers looked protective in heart failure with advanced kidney disease — read that carefully

Design

Retrospective cohort, multivariable Cox regression with inverse probability of treatment weighting

Population

1,835 patients with heart failure and eGFR ≤30 mL/min/1.73 m², single tertiary centre, 2014–2025

Primary outcome

All-cause mortality from a national registry

Effect

HR 0.85 (95% CI 0.73–0.99) for calcium channel blocker use after weighting; 69.7% died over median 1.68 years

In 1,835 consecutive patients with heart failure and an estimated glomerular filtration rate of 30 mL/min/1.73 m² or less at a national referral centre, 53.8% were on a calcium channel blocker. Over a median 1.68 years, 69.7% died. Calcium channel blocker use was associated with lower all-cause mortality, with a hazard ratio of 0.85 (95% CI 0.73–0.99) after inverse probability of treatment weighting.

The subclass result is where scepticism becomes necessary. The association reached significance for non-dihydropyridine agents — verapamil and diltiazem — and not for dihydropyridines. Non-dihydropyridine calcium channel blockers are negatively inotropic and are conventionally avoided in heart failure with reduced ejection fraction. A finding that they track with better survival in a heart failure cohort is more readily explained by which patients receive them than by what they do: a physician prescribes verapamil or diltiazem to a patient with preserved ejection fraction or atrial fibrillation, and avoids it in the patient with a dilated, failing ventricle.

That is confounding by indication, and weighting on measured covariates does not remove it when the unmeasured covariate is the clinician's judgement about the ventricle. The honest conclusion from this dataset is narrower than the authors': calcium channel blockers used for blood pressure control in this population were not associated with harm.

• Do not start a non-dihydropyridine calcium channel blocker in heart failure with reduced ejection fraction on the strength of this
• Where one is already in place for rate control, this is mild reassurance about continuing it
• Ejection fraction and the indication for the drug are the two variables that would explain this result, and neither is adequately captured
• A 69.7% mortality over 1.68 years tells you how sick this cohort is — most therapeutic questions here are about symptoms, not survival
• Blood pressure control in advanced chronic kidney disease with heart failure remains a legitimate use of a dihydropyridine

Why it matters

A conclusion that contradicts established pharmacology usually means the study design, not the pharmacology, is what needs explaining.

Don't overread it

Retrospective and single centre. The association is not causal, and the subclass finding runs against the known negative inotropy of verapamil and diltiazem in reduced ejection fraction.

The statistics, in plain English

A hazard ratio of 0.85 with an upper confidence limit of 0.99 is a result sitting on the boundary of significance: shift a few deaths between groups and it crosses 1.0. Inverse probability of treatment weighting balances the confounders that were recorded. It cannot balance the reason a cardiologist chose verapamil for this patient and not that one, which is precisely the variable driving both the prescription and the prognosis.

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