Diastolic heart failure (or cor pulmonale) refers to the development of right ventricular heart failure due to diseases of the chest wall or the lungs that impair breathing sufficiently to lower blood oxygen and raise carbon dioxide levels. These two gas exchange abnormalities can work separately, or synergistically, to raise pulmonary artery pressure (pulmonary hypertension). Many intrinsic lung disorders can cause diastolic heart failure, including lung blood clots (pulmonary embolism), COPD, interstitial lung diseases, either idiopathic or due to autoimmune disorders, or extensive scarring from infections, as in cystic fibrosis, tuberculosis or other inflammatory diseases. In post-polio and other neuromuscular disorder patients, diastolic heart failure follows prolonged hypoventilation with both hypoxemia and hypercarbia which cause pulmonary vascular hypertension, increasing the work of the right ventricle just as systemic hypertension increases the work of the left ventricle. When the right ventricle can no longer compensate by increasing the force of contraction, it fails. This failure then resists blood coming to the heart and backs up, causing swelling of the liver, fluid buildup in the abdomen (ascites) and extremity edema. The neck veins will swell, as well.
While this condition is not common in polio survivors, it is more likely to occur in those who needed iron lung ventilation at the onset of polio. Since polio is usually asymmetric, the unequal muscle forces over time result in marked chest and spinal abnormalities. This leads to a greater likelihood to hypoventilate (see Underventilation), especially when supine, as during sleep. Use of an iron lung during acute polio could be an indicator of the potential to develop hypoventilation. An early warning for diastolic heart failure may be signs of a confused state. Later, fluid retention, usually with ankle swelling, will occur.
Diagnostic studies may include electrocardiogram, chest x-ray, and arterial blood gas tests for low blood oxygen. Treatment for cor pulmonale requires oxygen therapy for at least 12 hours (during the night). Using oxygen alone can be dangerous for post-polio/neuromuscular patients as O2 shuts off the intrinsic sensors for low oxygen levels that stimulate breathing rate, thus worsening underventilation and, if unmonitored, leads to CO2 narcosis (Dying Pink). Sometimes diuretic treatment plus restriction of salt is needed. For some, digitalis preparations and anti-arrhythmic medications may be needed for irregularities in the heartbeat. Potassium supplementation may be needed & prescribed to replace that lost through the kidneys during the diuretic therapy as potassium loss increases muscle weakness (Cohn, 2000).
Many more effective agents are now used to treat diastolic heart failure selected for each patient based on their characteristics and may include angiotensin-converting enzyme inhibitors (ACE inhibitors–the generic drug name usually ends in “pril”), angiotensin receptor blockers (called ARBs and generic name usually ends in “artan”), and beta-blockers (generic name usually ends in “olol”). In addition, statins may be used for high cholesterol levels.
An increase of carbon dioxide cannot be managed with oxygen therapy alone, and requires assisted ventilation. All post-polio/neuromuscular patients with hypoventilation develop sleep irregularities. They need to be assessed with a sleep study (polysomnography) to determine if assisted ventilation is needed rather than oxygen alone. Giving oxygen alone when hypoventilation is present can allow a dangerous buildup of carbon dioxide and lead to life-threatening respiratory failure with acidosis (see above).
CPAP is used for obstructive upper airway causes of hypoventilation. Upper airway obstruction can occur along with respiratory muscle failure, but CPAP is then useful only if the obstruction is the dominant reason for underventilation. Post-polio/neuromuscular patients need volume expansion of the chest and not an intervention (CPAP) that struts the upper airway.
The frequency of this complication is not well researched or well documented. Polio survivors often develop spinal deformities, such as scoliosis and kyphosis, due to asymmetrical paralytic involvement of chest muscles and diaphragms; and asymmetry of the chest and lungs increases the work of breathing due to uneven airflow patterns. Thus, the presence of spinal deformities is a risk factor for developing respiratory failure and right-sided heart failure.
When hypoxemia and respiratory acidosis is corrected, pulmonary hypertension is relieved. This reduces right ventricular workload back to normal, “resting” the heart.
Reference
Cohn J.N., Kowey P.R., Whelton P.K., & Prisant L.M. (2000). New guidelines for potassium replacement in clinical practice: a contemporary review by the National Council on Potassium in Clinical Practice. Archives of Internal Medicine, 160(16), 2429-36.