Nuclear Medicine Department, S. Andrea Hospital, La Spezia, Italy.
Eur J Nucl Med Mol Imaging. 2013 Apr;40(4):548-57. doi: 10.1007/s00259-012-2323-5. Epub 2013 Jan 12.
Myocardial ischaemia is frequently silent in patients with type 2 diabetes. Although it has been proposed as a potential screening tool, the role of myocardial perfusion single photon emission computed tomography (MPS) has recently been questioned, due to the low prevalence of positive scans and the low rate of cardiac events. The aim of this study was to assess if pretest clinical variables can identify a subgroup of asymptomatic patients with type 2 diabetes at risk of silent myocardial ischaemia and a subsequent poor outcome
This prospective study included 77 patients (50 men, mean age 63 ± 9 years) with type 2 diabetes and no known coronary artery disease (CAD) or angina pectoris who underwent gated MPS to screen for CAD between March 2006 and October 2008. MPS images were interpreted using a semiquantitative visual 20-segment model to define summed stress, rest and difference scores. Ischaemia was defined as a sum difference score (SDS) ≥2. Patients were followed-up (median 4.1 years, range 0.8 - 6.1 years) and cardiac hard events (cardiac death or nonfatal myocardial infarction) were recorded.
Silent ischaemia was detected in 25 of the 77 patients (32 %). Specifically, 10 patients (13 %) had mild ischaemia (SDS 2 to ≤4) and 15 patients (19 %) had severe ischaemia (SDS >4). In univariate binary logistic analysis, microalbuminuria was the only significant predictor of silent ischaemia on MPS (odds ratio 4.42, 95 % CI 1.27 - 15.40; P = 0.019). The overall accuracy of microalbuminuria for predicting silent ischaemia was 71.4 % and was 89.6 % for predicting severe ischaemia. Kaplan-Meier curves showed no significant group differences in 5-year cardiac event-free survival between patients with and those without microalbuminuria, or between patients with SDS ≥2 and those with SDS <2. In contrast, 5-year event-free survival was significantly lower in patients with SDS >4 than in patients with SDS ≤4: 55.6 % (95 % CI 39.0 - 72.2 %) vs. 94.5 % (95 % CI: 91.4 - 97.6 %), respectively (Breslow test, chi-square 20.9, P < 0.001). Median cardiac event-free survival was not observed in the whole group, while the 25th percentile of cardiac event-free survival was reached only in patients with SDS >4 (2.3 years). In univariate Cox regression analysis, SDS >4 predicted cardiac event-free survival (hazard ratio 12.87, 95 % CI 2.86 - 27.98; P = 0.001), while SDS ≥2 did not (hazard ratio 2.78, 95 % CI 0.62 - 12.46, P = 0.16).
In this group of patients with type 2 diabetes, microalbuminuria was the only predictor of silent ischaemia on MPS. Assessment of microalbuminuria should be routinely considered among the first risk stratification steps for CAD in patients with type 2 diabetes, even though severe ischaemia on MPS is a major predictor of cardiac event-free survival.
2 型糖尿病患者常存在无症状心肌缺血。虽然心肌灌注单光子发射计算机断层扫描（MPS）已被提议作为一种潜在的筛查工具，但由于阳性扫描的低发生率和心脏事件的低发生率，其作用最近受到质疑。本研究旨在评估预先测试的临床变量是否可以识别出一组无症状 2 型糖尿病患者，这些患者存在无症状心肌缺血和随后不良预后的风险。
这项前瞻性研究纳入了 77 例（50 名男性，平均年龄 63 ± 9 岁）无已知冠状动脉疾病（CAD）或心绞痛的 2 型糖尿病患者，他们在 2006 年 3 月至 2008 年 10 月期间接受门控 MPS 筛查 CAD。使用半定量视觉 20 节段模型对 MPS 图像进行解读，以定义总和应激、休息和差异评分。缺血定义为总和差值评分（SDS）≥2。对患者进行随访（中位随访时间为 4.1 年，范围 0.8-6.1 年），并记录心脏不良事件（心脏死亡或非致死性心肌梗死）。
77 例患者中有 25 例（32%）检测到无症状性缺血。具体来说，10 例（13%）患者存在轻度缺血（SDS 2 至≤4），15 例（19%）患者存在严重缺血（SDS>4）。在单变量二元逻辑分析中，微量白蛋白尿是 MPS 上无症状性缺血的唯一显著预测因素（优势比 4.42，95%置信区间 1.27-15.40；P=0.019）。微量白蛋白尿预测无症状性缺血的总体准确率为 71.4%，预测严重缺血的准确率为 89.6%。Kaplan-Meier 曲线显示，微量白蛋白尿患者与无微量白蛋白尿患者之间、SDS≥2 患者与 SDS<2 患者之间，5 年心脏无事件生存率无显著差异。相反，SDS>4 的患者 5 年无事件生存率明显低于 SDS≤4 的患者：55.6%（95%置信区间：39.0-72.2%）与 94.5%（95%置信区间：91.4-97.6%），差异有统计学意义（Breslow 检验，卡方值 20.9，P<0.001）。整个组未观察到中位心脏无事件生存率，而 SDS>4 患者仅达到 25%的心脏无事件生存率（2.3 年）。在单变量 Cox 回归分析中，SDS>4 预测心脏无事件生存率（危险比 12.87，95%置信区间 2.86-27.98；P=0.001），而 SDS≥2 则不能（危险比 2.78，95%置信区间 0.62-12.46，P=0.16）。
在这组 2 型糖尿病患者中，微量白蛋白尿是 MPS 上无症状性缺血的唯一预测因素。即使 MPS 上存在严重缺血是心脏无事件生存率的主要预测因素，在对 2 型糖尿病患者进行 CAD 的最初风险分层步骤中，也应常规考虑微量白蛋白尿评估。
