Heart failure — the manual, from the day the reservoir overflows
In Between B1 and B2 we called the left atrium a reservoir. Congestive heart failure (CHF) is the day the reservoir overflows — pressure backs up until the lungs begin to flood, and the space for breathing shrinks.
Heavy material, but this article's purpose is a manual, not fear. CHF is a treatable emergency, and once the crisis passes and the cat comes home, the caregiver's skill largely determines both the length and the quality of the time that remains. From the emergency night to the daily routine after discharge, in order.
1. What has happened — the two ways the water rises
| Pulmonary oedema (inside the lungs) | Pleural effusion (outside the lungs, in the chest) | |
|---|---|---|
| What it is | The lung tissue itself soaks | Fluid pools between lungs and ribs and squeezes the lungs flat |
| Fast relief | Injectable diuretic + oxygen | Thoracocentesis — draining by needle frees the breathing within minutes |
| Course (2025 study) | Median survival 234 days | Median survival 155 days — the effusion form takes more work |
2. From signal to hospital
- Early (days ahead) — the sleeping rate climbing stepwise (20 → 26 → 33…), less activity, more hiding, fading appetite. Caught here, this can end as a clinic visit
- Emergency (now) — rate above 40, abdomen heaving with each breath, open-mouth breathing, pale or bluish tongue and gums, crouched with neck extended. → Hospital immediately
- Transport rule — minimal stimulation — a dyspnoeic cat can collapse from one burst of stress. Towel over the carrier, quiet, no restraining or repositioning, and call ahead so oxygen is ready on arrival
3. At the hospital — why "stabilise before testing" is correct
On arrival, the team may put the cat in an oxygen cage before any imaging. That is not delay — it is the standard of care. A dyspnoeic cat can die from something as small as being positioned for an X-ray, so the order is oxygen → mild sedation (butorphanol) → injectable diuretic → tests once stable. If effusion is found, it is drained — treatment and instant relief in one procedure.
The first 48–72 hours are the pass. Beyond it, many cats improve visibly within days and go home — usually with a simple discharge list: furosemide, clopidogrel, and "count the breaths at home."
4. The heart of home care — the diuretic tightrope
Ninety percent of post-discharge management is the diuretic. The principle is one sentence: "the lowest dose that keeps the lungs dry." Why lowest — diuretics cut blood flow to the kidneys and dehydrate. A 2024 study showed creatinine climbing with higher furosemide doses. Too much dries the lungs but wounds the kidneys; too little spares the kidneys but refloods the lungs.
The compass for this tightrope is the sleeping respiratory rate:
| Sleeping rate | Meaning | Action |
|---|---|---|
| Steadily under 30 | The current dose is working | Hold. If stability lasts, discuss trying a reduction |
| Creeping back up (several days running) | The lungs are refilling | Call the clinic — follow the pre-agreed adjustment rule if you have one |
| Above 40 / laboured | Relapse | Hospital that day |
- Recheck routine — kidney values and potassium within 1–2 weeks of starting or raising the dose; every 1–3 months once stable
- Water always free — never restrict drinking while on diuretics
- If the dose keeps climbing — needing more than 6 mg/kg/day without staying dry meets the definition of refractory (stage D), and the move is to a stronger diuretic (torasemide). The drug has not failed you; the disease has moved — and a switch often regains control
- If kidney values rise too — the heart-kidney bargaining begins, and your breathing-rate log is the evidence on the table (comorbidity article)
5. The supporting cast of drugs
| Drug | Role | Where the evidence stands |
|---|---|---|
| Furosemide | The lead — pulling water off the lungs | Standard. Section 4 is the whole story |
| Clopidogrel | Clot prevention | Effectively essential at stage C — an atrium that has failed is a high-clot-risk atrium (the clot article) |
| Pimobendan | Contractility support, vasodilation | Off-label in cats. Retrospective work links it to longer survival; no randomised trial. Caution with SAM (outflow obstruction) — clinics legitimately differ on using it |
| ACE inhibitors etc. | RAAS suppression | Weak evidence of benefit in feline CHF — adjunct |
| Torasemide | The stronger diuretic | The switch card for furosemide-refractory cases |
For households where pilling is a battle: refusals grow with pill count. Priority: diuretic > clopidogrel > the rest — agree in advance with your vet what to protect on the days when not everything goes in.
6. The cat whose chest keeps refilling — living with taps
- Thoracocentesis bears repeating — "again?" is not failure; it is how this form is managed
- The interval between taps is the key metric — 3 weeks → 2 → 1 signals progression; widening intervals are good news. Log each tap date in the app and watch the spacing
- Between taps the compass is still the breathing rate — the chest refills, and the rate rises first
7. Prognosis — the numbers, and this stage's real goal
Honestly: median survival after CHF scatters across studies from about five months to a year (234 days for oedema, 155 for effusion in the 2025 study). And as always the range is wide — cats living two or three good years exist, and what they mostly have in common is a caregiver who counts breaths.
The goal of this stage is not a number but the proportion of good days. A well-controlled CHF cat sleeps in the window again, demands meals, purrs. As long as that daily life holds, the treatment is succeeding — and for the day it stops holding, part 1 of this bible keeps the farewell chapter ready. Read once in advance, that day's decisions weigh less.
8. What to ask your vet
- "Is my cat the oedema form or the effusion form — or both?"
- "Above what rate do I call, above what rate do I come in? Can we set a pre-agreed adjustment rule?"
- "When do we recheck kidneys and potassium after starting the diuretic?"
- "If the rate stays stable for a long stretch, can we try lowering the dose?"
- "Would pimobendan help or harm this particular cat (given SAM status)?"
- "On a day when I cannot get every pill in, which drug comes first?"
9. Related
- Resting respiratory rate — this article's compass: method and traps
- The clot (ATE) — stage C's other face
- Feeding the heart-disease cat — electrolytes and calories in the diuretic era
- CKD with other diseases — the heart-kidney tightrope in detail