Congestive heart failure (CHF) primarily occurs when the heart cannot pump enough blood to meet the body’s demands or when the heart can only meet the body’s demands by pumping blood at a higher-than-normal filling pressure.1 While there can be an acute cause of CHF, it is frequently a slow, cumulative condition caused by work overload & fatigue or progressive loss of myocardium (a.k.a. heart muscle).2
Starling’s Law
Though not the first to do so, the physiologist Ernest Starling recognized the correlation between a muscle fiber being stretched & an ejection reaction. This correlation is known as “Starling’s Law.” He noted when muscle fibers are stretched, they react by contracting (due to autonomic nervous system sensory receptors in the muscle). He also recognized the strength of this contraction is dependent upon the length of the fiber.3 The heart muscle fibers are most lengthened at rest (during diastole – or dilation – when a chamber of the heart is refilling). In short, the heart (the atrium), when filled with blood, stretches & stretch receptors inside the muscle sense the filling & so react by contracting. The force of this contraction depends on the size of the load & on the muscle fibers being relaxed & lengthened (stretched) by the load.
As long as the heart remains strong, it can continue to pump blood effectively. However, after managing an increased load over an extended period of time, the heart begins to fatigue, reducing its contraction strength & the load it expels. Consequently, the body does not receive as much blood as it needs & the venous flow begins to back up. This increases pressure in the veins (which normally have a lower pressure) & forces fluid back into the tissues. Symptoms depend on which part of the heart is fatiguing. Eventually, the heart will fail. In some cases (depending on the reason), digitalis is effective.
Simplified Summary of Heart Failure
- Heart Failure due to Mechanical Insufficiency or “Low-Output Failure” – The volume is normal but the heart is impaired. Digitalis is effective.
- Heart Failure due to High-Output Failure or “Dynamic Insufficiency” – The heart is healthy but the volume is abnormal due to an underlying medical condition. When digitalis is given in this scenario, it will not help (the heart is already working as hard as it can).4 Examples include Grave’s Disease (the thyroid must be treated to reduce the cardiac load), arteriovenous fistula (the fistula must be removed) or anemia.
- Combination High & Low-Output failure – The underlying medical reason for increased volume will eventually cause damage to the heart, leading to mechanical insufficiency or low-output failure. If the primary cause is low-output (where the heart is impaired but can manage the volume load when resting), the patient will need to reduce activity to reduce overexertion which would increase the volume & lead to the High-Output & Low-Output combined form of heart failure.5
Simplified Summary of Lymphatic Failure
In a similar manner, a portion of the lymphatic structures (lymph angions) are often likened to hearts because they have smooth muscle & stretch receptors lining them, enabling them to contract when filled with lymph fluid.4 Interestingly, the lymphatic system is not only activated by the internal stretching due to increased internal angion pressure but also “by the external stretching stimulus produced by massage.”5 Just as digitalis is sometimes appropriate & helpful in certain cases of heart failure, manual lymph drainage is sometimes effective in cases of swelling, in particular, in lymphedema.
- Swelling due to Mechanical Insufficiency or “Low-Output Failure” (i.e. Lymphedema) – The volume is normal but the lymph structures are impaired. Manual lymph drainage is effective.
- Swelling due to “High-Output Failure” or “Dynamic Insufficiency” (i.e. Edema) – The lymphatic structures are normal but the volume isn’t. If manual lymph drainage is attempted in this scenario, it will not help (the lymphatic system is already working as hard as it can).6
- Combination Lymphedema & Edema or “Low & High-Output Failure” – Either there is an underlying medical cause contributing to an unusual excessive amount of volume that healthy lymph structures have been coping & eventually fatigue, or the impaired lymph structures have managed the usual volume but an unexpected event causes a volume increase (such as rigorous exercise, air travel, etc.) which overwhelms them.
References
1 Kumar, V., Abbas, A., Aster, J. (2013). Robbins Basic Pathology (9th ed.), location 18740. Pennsylvania: Elsevier Saunders.
2 Kumar, V., Abbas, A., Aster, J. (2013). Robbins Basic Pathology (9th ed.), location 18747. Pennsylvania: Elsevier Saunders.
3Starling EH. The Linacre Lecture on the Law of the Heart. London, UK: Longmans, Green and Co; 1918.
4 Foldi, M, Foldi, E. (2006). Foldi’s Textbook of Lymphology (2nd ed.), p. 209. Germany: Urban & Fisher.
5 Foldi, M, Foldi, E. (2006). Foldi’s Textbook of Lymphology (2nd ed.), p. 202. Germany: Urban & Fisher.
6 Foldi, M, Foldi, E. (2006). Foldi’s Textbook of Lymphology (2nd ed.), p. 212. Germany: Urban & Fisher.
