Cardiomyopathies
How faults in the heart muscle itself produce weak, dilated ventricles, thick and obstructed ones, stiff ones that will not fill, a right ventricle that turns to fat and scar, or a heart stunned by stress.
By the end, you can
- Relate the structure of the cardiac muscle cell, its sarcomeres and its intercalated discs to the genes and toxins that cause cardiomyopathy.
- Explain how dilated, hypertrophic and restrictive cardiomyopathies each disturb contraction or filling.
- Explain why outflow obstruction in hypertrophic cardiomyopathy is dynamic and how it changes the murmur.
- Explain how defective desmosomes in arrhythmogenic cardiomyopathy and a catecholamine surge in Takotsubo cardiomyopathy damage the heart.
- Recognise the classic appearances, classifications and tests of the cardiomyopathies, and explain how the main treatments act on each mechanism.
What it is
A cardiomyopathy is a disease in which the heart muscle itself is structurally and functionally abnormal, without coronary artery disease, high blood pressure, valve disease or congenital heart disease enough to explain it. Cardiomyopathies are described first by the shape and function of the heart (dilated, hypertrophic, restrictive, arrhythmogenic) and then by cause, genetic or acquired. Takotsubo cardiomyopathy is an acute, usually reversible form triggered by stress.
5 types to tell apart
- Dilated (DCM)
- The ventricles dilate and contract weakly. Genetic (titin, lamin A/C), toxic (alcohol, anthracyclines), peripartum or after myocarditis.
- Hypertrophic (HCM)
- Thick, hypercontractile, stiff left ventricle, often with outflow obstruction; usually from autosomal dominant sarcomere gene variants.
- Restrictive (RCM)
- Stiff ventricles of normal size that fill poorly; usually infiltrative, such as amyloid, sarcoidosis or iron overload.
- Arrhythmogenic (ARVC)
- Desmosome defects let muscle cells come apart and be replaced by fat and scar, mainly in the right ventricle, causing ventricular arrhythmias.
- Takotsubo (stress) cardiomyopathy
- Sudden, reversible stunning of the left ventricular apex after intense stress, mimicking a heart attack.
Normal function
Muscle cells joined to pull together
Heart muscle is built from cardiomyocytes: short, branched , each with one or two central , joined end to end at . Each disc holds three kinds of junction: desmosomes, which rivet neighbouring cells so they do not pull apart under strain; adherens junctions, which anchor the actin filaments of one cell to the next; and gap junctions, through which current spreads so that the muscle contracts as one.
Inside each cell, sarcomeres shorten as myosin heads pull on actin, switched on by calcium acting through troponin and tropomyosin. Titin, the largest protein in the body, runs through each sarcomere like a spring: it sets the resting stiffness of the muscle and helps it recoil after each beat. Other scaffold proteins link the sarcomeres to the cell membrane and the matrix outside (dystrophin) and to the nuclear envelope (lamin A/C).
The cells lie in orderly, parallel bundles so that their pull adds up, and the thickness of the wall and the size of each chamber match the load placed on them. Cardiomyocytes cannot divide: lost cells are replaced by scar, and overloaded cells can only enlarge. A cardiomyopathy begins when a faulty protein, a toxin, an infiltrate or inflammation damages this muscle directly.
Underlying change · Step 1 of 6
Dilated cardiomyopathy: a weak, enlarged heart
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 6
Hypertrophic cardiomyopathy: thick, overactive muscle
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 6
Restrictive cardiomyopathy: stiff walls that will not fill
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 6
Arrhythmogenic cardiomyopathy: cells that come apart
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 5 of 6
Takotsubo cardiomyopathy: a heart stunned by stress
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 6 of 6
Different routes to the same dangers
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .