Exertional dyspnea in congestive heart failure. Living longer and doing more?

Exercise Capacity Is Independent of Respiratory Muscle Strength in Patients with Chronic Heart Failure

Background: Exercise intolerance in patients with chronic heart failure (CHF) is associated with a number of factors, including breathlessness and respiratory muscle weakness. However, many studies reported controversial results, and as yet there is no study on Arabic patients with CHF. This study aimed to examine the impact of breathlessness and respiratory muscle strength on exercise capacity in Arabic patients with CHF. Methods: This was a cross-sectional study, involving 42 stable adult male patients with CHF with a reduced ejection fraction and 42 controls who were free from cardiorespiratory and neuromuscular diseases. Patients with CHF and the controls underwent respiratory muscle strength tests and a six-minute walk test (6MWT), and the measurements were taken. Dyspnea was recorded using the modified Medical Research Council (mMRC) scale, along with the number of comorbidities. Results: Patients with CHF and controls were similar in age and sex. Patients with CHF had a greater number of comorbidities, a higher dyspnea score, a lower 6MWT score, and lower respiratory muscle strength (p < 0.001). Only 7% of patients with CHF had weak inspiratory muscle strength (<60% of that predicted) and 40% terminated the 6MWT due to dyspnea. The 6MWT was associated with mMRC (rs = −0.548, p < 0.001) but not with respiratory muscle strength (p > 0.05). Conclusions: Exercise intolerance in patients with CHF was associated with dyspnea and was independent of respiratory muscle strength.

A novel hypothesis comprehensively explains shock, heart failure and aerobic exhaustion through an assumed central physiological control of the momentary cardiovascular performance reserve

BACKGROUND

Heart failure (HF) and shock are incomprehensively understood, inconclusively defined and lack a single conclusive test. The proceedings that preceded and triggered clinical manifestations are occult. The relationships in between different shock and HF types and between each HF type and its matched shock are poorly understood.

THE ASSUMED HYPOTHESIS

We suggest that HF and shock are attributed to a momentary cardiovascular performance reserve - "the reserve". The reserve is controlled through an assumed central physiological mechanism that continuously detects and responds accordingly--"the reserve control". The assumed reserve is maximal at rest, and decreases with aerobic activity. When it decreases to a given threshold the reserve control alerts by induces manifestations of dyspnea and fatigue enforcing activity decrease, follow which the manifestations dissolve. HF is a condition of low reserve at baseline; hence, fatigue and dyspnea are frequently experienced following mild activity. Shock is assumed to occur when the cardiovascular reserve deteriorates below a sustainable limit where the reserve control induces a salvage-sacrifice response, preserving vital organ perfusion while impairing microcirculation effective perfusion in non-vital organ in which it causes cellular hypoxia followed by the familiar devastating cascade of events seen in shock.

DISCUSSION AND CONCLUSIONS

The hereby hypothesis may comprehensively explain the heart failure - shock puzzle as no alternative theory had ever succeeded. It provides the missing link between the different types of HF as of shock and in between. The hypothesis poses a great prove challenge but opens new research and clinical possibilities.