Abstract
Coronary flow is normally autoregulated so that within wide limits of changes in perfusion pressure (which approximate to diastolic BP) blood flow to the heart remains constant. Thus, as perfusion pressure falls, the coronary arterioles dilate to maintain flow; under basal conditions a five-fold increase in coronary flow can occur, i.e. a flow reserve of five. Coronary flow reserve is markedly impaired in the presence of severe coronary artery stenosis and/or LVH. In the presence of severe stenosis and LVH a fall in perfusion pressure (DBP), which would be normally well tolerated, results in a fall of coronary flow, ECG changes and ventricular dysfunction (fall in ejection fraction instead of the usual increase). The above mechanisms underlie the J-curve relationship between DBP and myocardial infarction (MI) in high risk hypertensives. In the absence of overt coronary artery disease (CAD) and LVH, the lower the DBP the better. However in the presence of CAD and LVH lowering the DBP (phase 5) to below the low-mid 80s results in an increased frequency of MI.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
