Coronary sinus pH during percutaneous transluminal coronary angioplasty: early development of acidosis during myocardial ischaemia in man

Muscle LIM protein interacts with cofilin 2 and regulates F-actin dynamics in cardiac and skeletal muscle

The muscle LIM protein (MLP) and cofilin 2 (CFL2) are important regulators of striated myocyte function. Mutations in the corresponding genes have been directly associated with severe human cardiac and skeletal myopathies, and aberrant expression patterns have often been observed in affected muscles. Herein, we have investigated whether MLP and CFL2 are involved in common molecular mechanisms, which would promote our understanding of disease pathogenesis. We have shown for the first time, using a range of biochemical and immunohistochemical methods, that MLP binds directly to CFL2 in human cardiac and skeletal muscles. The interaction involves the inter-LIM domain, amino acids 94 to 105, of MLP and the amino-terminal domain, amino acids 1 to 105, of CFL2, which includes part of the actin depolymerization domain. The MLP/CFL2 complex is stronger in moderately acidic (pH 6.8) environments and upon CFL2 phosphorylation, while it is independent of Ca(2+) levels. This interaction has direct implications in actin cytoskeleton dynamics in regulating CFL2-dependent F-actin depolymerization, with maximal depolymerization enhancement at an MLP/CFL2 molecular ratio of 2:1. Deregulation of this interaction by intracellular pH variations, CFL2 phosphorylation, MLP or CFL2 gene mutations, or expression changes, as observed in a range of cardiac and skeletal myopathies, could impair F-actin depolymerization, leading to sarcomere dysfunction and disease.

Changes in coronary sinus pH during dipyridamole stress in patients with hypertrophic cardiomyopathy

OBJECTIVES

The presence of angina pectoris and myocardial scarring in patients with hypertrophic cardiomyopathy (HCM) suggests that myocardial ischemia is a factor in the pathophysiology of the disease. The clinical evaluation of ischaemia is problematic in HCM as baseline electrocardiographic abnormalities are frequent and thallium-201 perfusion abnormalities correlate poorly with anginal symptoms. Coronary sinus pH measurement using a catheter mounted pH electrode is a validated sensitive technique for the detection of myocardial ischaemia.

METHODS AND RESULTS

11 patients with HCM and chest pain (eight men; mean (SD) (range) age 36 (11) (19-53) years) and six controls (two men; mean (SD) (range) age 49 (11) (31-62) years) with atypical pain and normal coronary angiograms were studied. Eight patients with HCM had baseline ST segment depression of > or = 1 mm and four had reversible perfusion defects during stress 201TI scintigraphy. A catheter mounted hydrogen ion sensitive electrode was introduced into the coronary sinus and pH monitored continuously during dipyridamole infusion (0.56 mg/kg over four min). The maximal change in coronary sinus pH during dipyridamole stress was greater in patients with HCM than in controls (0.082 (0.083) (0 to -0.275) v 0.005 (0.006) (0 to -0.012), P = 0.02). In six patients (four men; mean (SD) (range) age 29 (9) (19-40 years) the development of chest pain was associated with a gradual decline in coronary sinus pH (mean 0.123 (0.089)), peaking at 442 (106) s. There were no relations among left ventricular dimensions, maximal wall thickness, and maximum pH change. In patients with HCM there was a correlation between maximum pH change and maximum heart rate during dipyridamole infusion (r = 0.70, P = 0.02).

CONCLUSION

This study provides further evidence that chest pain in patients with HCM is caused by myocardial ischaemia. The role of myocardial ischaemia in the pathophysiology of the disease remains to be determined but coronary sinus pH monitoring provides a method for quantifying and prospectively assessing its effects on clinical presentation and prognosis.

The ST segment--the herald of ischaemia, the siren of misdiagnosis, or syndrome X?

Syndrome X is the term applied to patients with anginal-type chest pain who, despite a positive exercise stress test, have angiographically normal coronary arteries. Such patients probably belong to a heterogeneous group, and in a proportion the exercise test is falsely positive. With the availability of more accurate techniques for the detection of myocardial ischaemia, it is apparent that some patients can be shown to develop transient myocardial ischaemia with stress. The paradox of normal coronary arteries and a positive exercise test may be resolved by improved understanding of the regulatory control of regional myocardial blood flow, particularly at the level of the microvasculature, and of the metabolic expression of myocardial ischaemia.

Coronary venous noradrenaline during coronary angioplasty

Coronary venous and arterial noradrenaline concentrations were measured during percutaneous transluminal coronary angioplasty in 14 patients. Coronary venous noradrenaline did not increase significantly during balloon inflation but was increased during early reperfusion in patients undergoing left anterior descending angioplasty (n = 8), from 157 +/- 38 pg/ml to 295 +/- 94 pg/ml (P less than 0.05). Coronary blood flow, measured by thermodilution in 7 further patients during left anterior descending angioplasty, was 69 +/- 9 ml/min, decreased to 80 +/- 3% of basal flow during balloon inflation (P less than 0.01) and increased to 135 +/- 5% during early reperfusion (P less than 0.01). It was estimated using these results that cardiac spillover of noradrenaline did not change during occlusion of the left anterior descending artery, but increased almost 3-fold during early reperfusion. During the period of balloon inflations, there was a modest increase in overall sympathetic tone, as assessed by total noradrenaline spillover to plasma (400 +/- 77 ng/min to 473 +/- 87 ng/min, P less than 0.01). These results, suggesting an increase in release of noradrenaline during early reperfusion following brief occlusion of the left anterior descending artery, may be relevant to the genesis of reperfusion arrhythmias.