Weatherly's Woes - Heart Failure

CARDIAC HYPERTROPHY

“His heart grew three sizes that day”

Cardiac Hypertrophy is the adaptive growth of heart muscle. Just like your biceps, the heart can grow larger if it has to do more work. This commonly occurs with hydrostatic stress (high pressure from hypertension, for example) or with a high sympathetic tone. This is a normal, healthy response . . . at first. If the heart grows too large, it loses efficacy, and heart failure ensues. When cardiac hypertrophy turns harmful, we refer to it as cardiomyopathy. A fundamental problem with cardiomyopathy is that the muscle growth is not accompanied by a proportional growth in capillaries, which makes the enlarged heart more vulnerable to ischemia, CHF and death.

There are two different kinds of cardiac hypertrophy: Hypertrophic and Dilated.

CARDIOMYOPATHY

Heart muscle disease

DILATED CARDIOMYOPATHY is the dilation of the chambers. The walls stretch out and become floppy and weak. CO plummets. This is systolic heart failure. Stretching of the valves can result in regurgitant valves. Stretching of the myocytes can result in arrhythmias. It’s most commonly idiopathic; other causes include genetic mutations (AD mutation of Titin protein), myocarditis (Coxsackie / Chagas), alcoholism, wet beriberi (B1 deficiency), drugs (Doxorubicin, cocaine) and pregnancy. There isn’t a good treatment. An LVAD device can hold you over until a heart transplant. On EKG, the QRS spikes will be tall (more muscle)

HYPERTROPHIC CARDIOMYOPATHY is the growth of the walls. The huge muscle protrudes into the LV chamber, limiting diastolic filling. The beefy wall also loses flexibility and compliance. This decreases LV end diastolic volume (LVEDV), thus limiting CO. This is diastolic heart failure. Most commonly due to AD genetic mutations in myosin proteins, hypertension and Friedreich's Ataxia.

There is another condition called HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY where the muscle growth is limited to the interventricular septum. This is a problem because contraction makes the muscle widen further, and it can obstruct the Aortic valve. The heart beats faster and harder during exercise, which leads to symptom flares with exercise. Symptoms are due to the drop in CO to the brain, namely syncope. This is a genetic condition, it is often diagnosed in teenage athletes. Unfortunately, the terminology around this is frustrating. Many call it simply “Hypertrophic Cardiomyopathy.” On biopsy, there will be myofiber hypertrophy and disarray. There is a murmur that is similar to Aortic Stenosis. But there’s a big difference. If you increase LV volume (handgrip increases afterload, leg raise increases preload), the thiqq septum will be pushed apart from the LV outlet, quieting the HOCM murmur. In Aortic Stenosis, more LV volume means more blood will whoosh past the stenotic valve, making the murmur louder.

HOCM

Restrictive Cardiomyopathy is the decreased compliance of the ventricles. The stiff ventricles cannot fill with blood during diastole. Caused by the deposition of biomolecular trash into the myocardium: amyloid protein (Amyloidosis), granulomas (Sarcoidosis), iron (Hemochromatosis) or eosinophilic fibrosis in the myocardium (Löffler Syndrome). They will present as diastolic CHF, but two signs differentiate them from Hypertrophic Cardiomyopathy: auscultation reveals a cardiac knock (which sounds just like an S3 sound) and small QRS spikes on EKG.

HEART FAILURE

Low cardiac output

Heart Failure refers to a heart that pumps poorly. Across the bajillion different categorizations, there is the consistent element: low cardiac output.

Timing of CHF

Most of the time CHF is asymptomatic. Patients live fairly normal lives, aside from exercise intolerance. Their CO is low, and their hearts are stressed out, but their body can compensate (RAAS, SNS). But sometimes CHF flares up. Flare ups are usually caused by excessive sodium intake -- the body is great at absorbing salt, but very bad at getting rid of it. To normalize the sodium concentration, the body retains some extra water (using ADH). Healthy patients can distribute that extra water evenly across their entire circulatory system. But with heart failure, the fluid gets backed up behind the shoddy pump (heart). That extra water (hypervolemia) causes all of the classic symptoms of heart failure. Symptoms occur “upstream” from the failing heart. This will hopefully become clear over the next few pages.

Diagnosis of CHF

The gold standard is the clinical gestalt of a cardiologist. Other tests include an elevated BNP (Brain Natriuretic Peptide) and an abnormal Echo (you don’t have to interpret Echos).

Categories of CHF

There are two ways to think about CHF classification.

Left vs Right - different symptoms
Systolic vs Diastolic - same symptoms, but different pathophysiology

SYSTOLIC Heart Failure

The heart muscle is weak. Part of the heart wall dies, leaving an inert scar. The Ejection Fraction is low (<45%), AND the stroke volume is low. Most common cause: MI. Next most common cause is dilated cardiomyopathy.

DIASTOLIC Heart Failure

The heart can pump, but it can’t refill. As the heart muscle becomes beefier, it loses compliance and starts growing into the chamber, leaving less room for blood. Look at this thiccy. The Ejection Fraction is normal (45 - 65%), but the stroke volume is low. Most common cause: Hypertension

Right Heart Failure

Less common. If due to lung disease (pulmonary hypertension) it’s called cor pulmonale.

Left Heart Failure

Left CHF causes lung symptoms at first, then it will cause Right CHF.

Note - most cases of real-world cases of CHF involve both sides

CHF TREATMENT

Acute CHF Treatment -- the goal is to remove fluid. Diuretics put fluid into pee, Nitrates allow more room for fluid in veins.

- - Loop Diuretic (Furosemide / Ethacrynic Acid). ALWAYS start them on a Loop.. Loop Diuretics are rapid-acting and strong. Loop Diuretics work by blocking the Na/K/2Cl transporter in the ascending Loop of Henle. SEs include hypokalemia, hypomag, hyperuricemia, sulfa allergies (Furosemide only), interstitial nephritis and ototoxicity. And of course, dehydration.
  - Nitrates. ALWAYS Use Nitrates to draw pulmonary edema away by opening up veins (lowers preload)
  - Hydralazine. Sometimes use Hydralazine to draw pulmonary edema away by opening up arteries (lowers afterload)
  - Inotropes. For very sick patients with SYSTOLIC failure, start an Inotrope (Dobutamine, Milrinone) drip to get that cardiac output up. For safety reasons, these drugs are only allowed to be given in the ICU.

Chronic CHF Treatment - The goal is to prevent the heart from (a) undergoing further pathological cardiomyopathy or (b) prevent further cardiac ischemia. Since cardiomyopathy is driven by a high sympathetic and RAAS tone, drugs that lower sympathetic and RAAS tone are the most effective at preventing further tissue growth.

- - ACE Inhibitors or ARBs will put a brake on the overfiring RAAS. These are 1st line drugs. They improve mortality. By lowering afterload and preload, these drugs prevent remodeling of the heart. SEs include angioedema, chronic cough and hyperkalemia.
  - Beta-blockers to block beta-1 adrenergic receptors. They improve mortality. They will slow down the heart rate and decrease inotropy. They improve preload and reduce myocardial oxygen demand. Use the selective BBs: Metoprolol, Carvedilol and Bisoprolol. WILL WORSEN ACUTE CHF.
  - Aldosterone Receptor Blockers (Spironolactone / Eplerenone) improve mortality in CHF! Like ACE Inhibitors, they prevent remodeling. Look out for hyperkalemia. Spironolactone can cause some unique SEs because it's a synthetic steroid. It blocks 17a-hydroxylase, preventing the synthesis of Testosterone. That leads to gynecomastia and impotence :(
  - Thiazide Diuretics. Thiazides are first-line for high blood pressure, but they work here too. Hydrochlorothiazide (HCTZ) is the prototypical Thiazide, but the newer Chlorthalidone might be superior. Thiazides are combined with Hydralazine in Black patients. Thiazides work on the DCT, blocking salt reabsorption. Peeing out salt and water is really helpful in CHF. SEs include hypercalcemia, hyperglycemia, hyperlipidemia, hyperuricemia, hypokalemia, hyponatremia, dehydration.
  - ENaC Blockers (Amiloride / Triamterene) block natriuresis at the end of the nephron. Look out for hyperkalemia. Not high yield.
  - Digoxin (the only oral inotrope) used to be the mainstay for severe systolic failure, but it’s rarely used nowadays -- it doesn’t improve mortality and it’s very tricky to safely dose. See the Other Antiarrhythmic page for more details.
  - New drugs
    - - Neprilysin Inhibitors (Sacubitril) stop the breakdown of ANP / BNP, which have the opposite effects of Angiotensin II. ANP is stronger than BNP, but BNP lasts longer (so it’s a better lab test). ANP / BNP are released by cardiomyocytes when the heart gets too full. The atria release ANP, while the ventricles release BNP. The drug companies usually combine this with Valsartan and market it as Entresto.
      - Ivabradine slows down the heart rate. It works by inhibiting the funny current (phase 4) of the SA node.
  - Optional Devices
    - - Implantable Cardiac Defibrillators are used in patients with a high risk for V-fib.
      - Biventricular Pacemakers are used in select patients to restore normal cardiac activity.