Activation of ß1 receptors and aII receptors along with stretch of the cell membrane trigger signaling cascades. Under some conditions these triggers lead to effective hypertrophy and an increase in size and function, and in others they trigger apoptotic cell death. AII, Angiotensin II; cAMP, cyclic adenosine monophosphate; DAG, diacylglycerol; IP3, 1,4,5-inositol trisphosphate; NE, norepinephrine; RAAS, renin-angiotensin-aldosterone system; SNS, sympathetic nervous system. New York Heart Association classification, based on functional capacity of the patient. Patients may go back and forth btwn. stages, depending on symptoms.
Class I (No Incapacity). No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, or dyspnea (shortness of breath).
Class II (Slight Limitation). Slight limitation of physical activity. Comfortable at rest, but ordinary physical activity results in fatigue, palpitation, or dyspnea.
Class III (Incapacity with Slight Exertion). Marked limitation of physical activity. Comfortable at rest, but less than ordinary activity (slight exertion) causes fatigue, palpitation, or dyspnea.
Class IV (Incapacity with Rest). Unable to carry out any physical activity without discomfort. Symptoms of cardiac insufficiency at rest. If any physical activity is undertaken, discomfort is increased.