Measurement of Myocardial Lactate Production for Diagnosis of Coronary Microvascular Spasm

Summary

Myocardial lactate production (coronary arterial-venous difference in serum lactate level) during coronary spasm provocation testing is considered as a highly sensitive marker that reflects acetylcholine-induced myocardial ischemia due to microvascular spasm. This article presents the procedures to assess myocardial lactate production for the diagnosis of coronary microvascular spasm.

Abstract

In about a quarter of patients with angina and non-obstructive coronary arteries, no epicardial spasm is noted on coronary arteriography during an angina attack. Since the pressure-rate product is almost identical at rest and the onset of attack in those patients, the decrease in coronary blood flow rather than increased myocardial oxygen consumption is likely to explain myocardial ischemia, indicating a substantial involvement with coronary microvascular spasm (MVS). Myocardial lactate production, which could be defined as a negative myocardial lactate extraction ratio (ratio of the coronary arterial-venous difference in lactate concentration to arterial concentration), is considered indicative of objective evidence to support the emerging myocardial ischemia. Thus, monitoring of the myocardial lactate production and the emergence of chest pain and ischemic electrocardiographic changes during acetylcholine (ACh) provocation testing is of significant value for detecting the entity of MVS. Practically, 1 min after incremental doses of ACh (20, 50, and 100 μg) are administered into the left coronary artery (LCA), paired samples of 1 mL of blood are collected from the LCA ostium and coronary sinus for measurement of lactate concentration by a calibrated automatic lactate analyzer. Then, the development of MVS could be confirmed by negative myocardial lactate extraction ratio despite the absence of angiographically demonstrable epicardial coronary spasm or before its occurrence throughout ACh provocation testing. In conclusion, assessment of myocardial lactate production is essential and valuable for the diagnosis of MVS.

Introduction

Recent studies demonstrated that ischemia with non-obstructive coronary arteries (INOCA) is caused mainly by functional coronary vasomotion disorders, including epicardial and microvascular spasms¹. The diagnosis of coronary vasoconstrictor dysfunction at the epicardial and/or microvascular levels often requires intracoronary provocation testing with a pharmacological vasoactive agent such as acetylcholine (ACh) during coronary angiography². Many patients with INOCA have no epicardial spasm on coronary arteriography despite the development of angina attack and ischemic electrocardiographic (ECG) changes in response to in....

Protocol

The measurement of myocardial lactate production during ACh provocation testing to evaluate coronary vasoreactivity was conducted following the ethical principles in the Declaration of Helsinki, and the protocol was approved by the Ethics Committees of Tohoku University (No.2016-1-643). All the patients provided written informed consent before the procedure. In this article, ACh provocation testing was performed following the guidelines of the Japanese Circulation Society⁹.

1. Preparation for the procedure

1. Ensure that the measurement of myocardial lactate production is performed in patients undergoing ACh....

Results

A 56-year-old woman with no coronary risk factors suffered from transient chest discomfort at rest. She underwent ACh provocation testing and measurement of myocardial lactate production for diagnosis of MVS. As shown in Figure 2, chest pain, ischemic ECG changes, and negative LER were noted immediately following 100 µg of ACh administration into the LCA. Still, no relevant epicardial coronary spasm was observed on angiography. Thus, she was diagnosed as having MVS. Intriguingly, she ha.......

Discussion

Detection of enhanced coronary vasoconstriction is possible by an additional pharmacological provocation testing with ACh or ergometrine during coronary angiography. Even now, there is no technique to directly visualize the coronary microvasculature for evaluation of its function in vivo, the occurrence of coronary spasm at microvascular level could be solely deduced by the reproduction of usual symptoms together with ischemic ECG changes despite the absence of epicardial coronary spasm during ACh provocation te.......

Materials

Name	Company	Catalog Number	Comments
ABL8000 FLEX blood gas analyzer	RADIOMETER, Copenhagen, Denmark	k041874	The automatic lactate analyzer
OUTLOOK	Terumo Corp, Tokyo, Japan	RQ-5JL4000	The Judkins-left catheter for coronary angiography
Ovisot for injection	Daiichi sankyo company, limited, Tokyo, Japan	871232	Injectable product of acetylcholine chloride for acetylcholine provocation testing
Supersheath	MEDIKIT CO., LTD., Tokyou, Japan	CS50P11TSM	The sheath for insertion of a catheter
Technowood SoftNAV Catheter	Technowood Corp, Tokyo, Japan	H710-FL445SH	The Amplatz-left catheter for blood sampling from coronary sinus