Evaluation of metoprolol versus diltiazem for rate control of atrial fibrillation in the emergency department

ObjectiveThe purpose of this study was to compare the effectiveness and safety of the metoprolol and diltiazem administration in the Emergency Department (ED) for rate control of supraventricular tachycardia.MethodsThis was a retrospective cohort study of adult patients who presented to the ED with ventricular rates ≥120 beats per minute (bpm) and who received bolus doses of either intravenous metoprolol or intravenous diltiazem. The primary outcome was achievement of rate control, defined as heart rate < 110 bpm, at two hours after administration of the last bolus dose of metoprolol or diltiazem. Safety outcomes included occurrence of hypotension, defined as systolic blood pressure < 90 mmHg or diastolic blood pressure < 60 mmHg, and bradycardia, defined as heart rate < 60 bpm.ResultsThere were 166 patients receiving metoprolol and 183 patients receiving diltiazem included in the study. The primary outcome, rate control at two hours after the last bolus dose of metoprolol or diltiazem was similar between the two groups (45.8% vs 42.6%, p = 0.590, respectively). The percentage of patients achieving rate control was also similar (47.0% vs 41.6%, p = 0.333) at one hour. At 0.5 h HR had a significantly greater numerical (diltiazem: 29.3 ± 23.1 bpm vs metoprolol: 21.8 ± 18.9 bpm, p = 0.012) and percent decrease (21.1% vs 15.94%, p = 0.014) in the diltiazem group compared to metoprolol. There was no significant difference in occurrence of bradycardia in the two groups (diltiazem: 3.83% vs metoprolol: 1.2%, p = 0.179). More patients in the diltiazem group compared to the metoprolol group experienced hypotension (39.3% vs 23.5%, p = 0.002). The difference in systolic hypotension events was not significantly different (9.29% vs 5.42%, p = 0.221), while the difference in diastolic hypotension events was significantly different (37.7% vs 22.3%, p = 0.002).ConclusionThere was no difference in acute rate control effectiveness two hours after the last bolus dose of diltiazem and metoprolol for supraventricular tachycardias. There was a significantly higher occurrence of hypotension in the diltiazem group which was driven by higher rates of diastolic blood pressures less than 60 mmHg.     

双源CT冠状动脉成像的重建时相及其与心率的相关性

目的 探讨双源CT(DSCT)冠状动脉成像的最佳重建时相及其与心率的相关性.方法 163例患者接受DSCT冠状动脉成像检查,选择自动化最佳舒张期和最佳收缩期重建模式,按美国心脏协会(AHA)分类指南将冠状动脉树分为15个节段,分3级评价图像质量.分析冠状动脉成像重建的最佳舒张期和最佳收缩期时相位置,采用Pearson相关分析评价其与心率的相关性.结果 163例患者平均心率为(69.3±14.6)次/分,冠状动脉成像重建的最佳舒张期时相为(75.5±4.6)% R-R间期,最佳收缩期时相为(36.4±4.5)% R-R间期;最佳舒张期、最佳收缩期时相的位置与心率分别存在相关性(r=0.307、0.579,P均<0.05);单一最佳时相重建时,总体冠状动脉图像质量得分为(1.06±0.22)分.结论 DSCT冠状动脉成像质量存在两个高峰期,即舒张中期和收缩中晚期;随着心率的增高,最佳舒张期时相位于舒张中期越晚的时相,最佳收缩期时相位于收缩中晚期越晚的时相.     

Prospectively versus retrospectively ECG-gated 256-slice coronary CT angiography: image quality and radiation dose over expanded heart rates

To compare image quality and radiation dose estimates for coronary computed tomography angiography (CCTA) obtained with a prospectively gated transaxial (PGT) CT technique and a retrospectively gated helical (RGH) CT technique using a 256-slice multidetector CT (MDCT) scanner and establish an upper limit of heart rate to achieve reliable diagnostic image quality using PGT. 200 patients (135 males, 65 females) with suspected coronary artery disease (CAD) underwent CCTA on a 256-slice MDCT scanner. The PGT patients were enrolled prospectively from January to June, 2009. For each PGT patient, we found the paired ones in retrospective-gating patients database and randomly selected one patient in these match cases and built up the RGH group. Image quality for all coronary segments was assessed and compared between the two groups using a 4-point scale (1: non-diagnostic; 4: excellent). Effective radiation doses were also compared. The average heart rate ± standard deviation (HR ± SD) between the two groups was not significantly different (PGT: 64.6 ± 12.9 bpm, range 45–97 bpm; RGH: 66.7 ± 10.9 bpm, range 48–97 bpm, P = 0.22). A receiver-operating characteristic (ROC) analysis determined a cutoff HR of 75 bpm up to which diagnostic image quality could be achieved using the PGT technique (P < 0.001). There were no significant differences in assessable coronary segments between the two groups for HR ≤ 75 bpm (PGT: 99.9% [961 of 962 segments]; RGH: 99.8% [1038 of 1040 segments]; P = 1.0). At HR > 75 bpm, the performance of the PGT technique was affected, resulting in a moderate reduction of percentage assessable coronary segments using this approach (PGT: 95.5% [323 of 338 segments]; RGH: 98.5% [261 of 265 segments]; P = 0.04). The mean estimated effective radiation dose for the PGT group was 3.0 ± 0.7 mSv, representing reduction of 73% compared to that of the RGH group (11.1 ± 1.6 mSv) (P < 0.001). Prospectively-gated axial coronary computed tomography using a 256-slice multidetector CT scanner with a 270 ms tube rotation time enables a significant reduction in effective radiation dose while simultaneously providing image quality comparable to the retrospectively gated helical technique. Our experience demonstrates the applicability of this technique over a wider range of heart rates (up to 75 bpm) than previously reported.     

Relationship Between Exercise Heart Rate and Age in Men vs Women

ObjectiveTo analyze a large cohort of patients who underwent exercise testing and also report sex differences in other exercise heart rate (HR) parameters to determine whether separate sex-based equations to predict peak HR are indicated.Patients and MethodsPatients aged 40 to 89 years who performed treadmill exercise tests (Bruce protocol) from September 21, 1993, to December 20, 2010, were included. Patients with cardiovascular disease or taking HR-attenuating drugs were excluded. After analyses on preliminary cohort, peak HR–modifying factors were eliminated to obtain a pure data set. Analysis of variance was used to test difference in HR responses by sex with age adjustment.ResultsA total of 37,010 patients (67.3% men) were included in the preliminary cohort. Men had higher peak HR (166±17 vs 163±16 beats/min [bpm]; P<.001), HR reserve (90±19 vs 84±17 bpm; P<.001), and HR recovery (19±8 vs 18±9 bpm; P<.03). Poor exercise capacity, current smoking, diabetes, and obesity had significant peak HR–lowering effects (all P<.001). In a pure cohort of 19,013 patients (51.3% of full cohort) without these factors, regression lines approximated more closely the traditional line of 220 – age. For men, the regression line in our final cohort was peak HR = 220 – 0.95 × age. For women, both slope (0.79 bpm/y) and intercept (210 bpm) were still substantially different from those obtained with the traditional formula.ConclusionThe HR responses to exercise are different in men and women. The HR response of men was close to that obtained with the traditional formula, but peak HR in women had a lower intercept and decreased more slowly with age. A separate formula for peak HR in women appears to be appropriate.     

Diurnal Heart Rate Patterns in Inappropriate Sinus Tachycardia

Background: Inappropriate sinus tachycardia (IAST) is a supraventricular tachycardia originating from the sinus node. Proposed etiologies for this symptom complex include autonomic dysfunction, abnormal automaticity, or hypersensitivity of the sinus node. Methods: Patients with IAST were identified by symptomatic tachycardia, with P‐wave morphology consistent with origination from a sinus location. A matched set of control subjects was included. Hourly heart rate (HR) was measured as the average HR during each one hour period on an ambulatory 24‐hour Holter monitor. Patients were further divided into two subgroups based on average daily HR ≤ 80 and >80 bpm. Harmonic analysis was used to evaluate diurnal variation. Results: The mean HR was 86.0 ± 12.8 beats per minute (bpm) in the IAST group and 73.9 ± 8.6 bpm in the control group (P = 0.056). There was an increased overall heart rate for the IAST group, which appeared to be more prominent in the morning hours. In the IAST subgroup with average daily HR ≤ 80, hourly HR appears similar to controls for the period 8 pm–8 am. However, in the late AM, the IAST group had an increase in HR not seen in the control subjects. In the IAST subgroup with average HR > 80, there appeared to be a fixed difference in HR compared to the control group, without hourly change. Conclusions: Patients with IAST and elevated average daily HR exhibit normal diurnal variation around a higher mean HR. In contrast, patients with IAST and lower average daily HR had an exaggerated morning rise in HR. These diurnal patterns may be useful to classify the pathophysiology of IAST. (PACE 2010; 911–919)     

High-pitch coronary CT angiography with third generation dual-source CT: limits of heart rate

To determine the average heart rate (HR) and heart rate variability (HRV) required for diagnostic imaging of the coronary arteries in patients undergoing high-pitch CT-angiography (CTA) with third-generation dual-source CT. Fifty consecutive patients underwent CTA of the thoracic (n = 8) and thoracoabdominal (n = 42) aorta with third-generation dual-source 192-slice CT with prospective electrocardiography (ECG)-gating at a pitch of 3.2. No β-blockers were administered. Motion artifacts of coronary arteries were graded on a 4-point scale. Average HR and HRV were noted. The average HR was 66 ± 11 beats per minute (bpm) (range 45–96 bpm); the HRV was 7.3 ± 4.4 bpm (range 3–20 bpm). Interobserver agreement on grade of image quality for the 642 coronary segments evaluated by both observers was good (κ = 0.71). Diagnostic image quality was found for 608 of the 642 segments (95 %) in 43 of 50 patients (86 %). In 14 % of the patients, image quality was nondiagnostic for at least one segment. HR (p = 0.001) was significantly higher in patients with at least one non-diagnostic segment compared to those without. There was no significant difference (p > 0.05) in HRV between patients with nondiagnostic segments and those with diagnostic images of all segments. All patients with a HR < 70 bpm had diagnostic image quality in all coronary segments. The effective radiation dose and scan time for the heart were 0.4 ± 0.1 mSv and 0.17 ± 0.02 s, respectively. Third-generation dual-source 192-slice CT allows for coronary angiography in the prospectively ECG-gated high-pitch mode with diagnostic image quality at HR up to 70 bpm. HRV is not significantly related to image quality of coronary CTA.     

Helical prospective ECG-gating in cardiac computed tomography: radiation dose and image quality

Helical prospective ECG-gating (pECG) may reduce radiation dose while maintaining the advantages of helical image acquisition for coronary computed tomography angiography (CCTA). Aim of this study was to evaluate helical pECG–gating in CCTA in regards to radiation dose and image quality. 86 patients undergoing 64-multislice CCTA were enrolled. pECG-gating was performed in patients with regular heart rates (HR) < 65 bpm; with the gating window set at 70–85% of the cardiac cycle. All patients received oral and some received additional IV beta-blockers to achieve HR < 65 bpm. In patients with higher or irregular HR, or for functional evaluation, retrospective ECG-gating (rECG) was performed. The average X-ray dose was estimated from the dose length product. Each arterial segment (modified AHA/ACC 17-segment-model) was evaluated on a 4-point image quality scale (4 = excellent; 3 = good, mild artefact; 2 = acceptable, some artefact, 1 = uninterpretable). pECG-gating was applied in 57 patients, rECG-gating in 29 patients. There was no difference in age, gender, body mass index, scan length or tube output settings between both groups. HR in the pECG-group was 54.7 bpm (range, 43–64). The effective radiation dose was significantly lower for patients scanned with pECG-gating with mean 6.9 mSv ± 1.9 (range, 2.9–10.7) compared to rECG with 16.9 mSv ± 4.1 (P < 0.001), resulting in a mean dose reduction of 59.2%. For pECG-gating, out of 969 coronary segments, 99.3% were interpretable. Image quality was excellent in 90.2%, good in 7.8%, acceptable in 1.3% and non-interpretable in 0.7% (n = 7 segments). For patients with steady heart rates <65 bpm, helical prospective ECG-gating can significantly lower the radiation dose while maintaining high image quality.     

Heart rate at baseline influences the effect of ivabradine on cardiovascular outcomes in chronic heart failure: analysis from the SHIFT study

Background

We analysed the effect of ivabradine on outcomes in heart failure (HF) patients on recommended background therapies with heart rates ≥75 bpm and <75 bpm in the SHIFT trial. A cut-off value of ≥75 bpm was chosen by the EMEA for approval for the use of ivabradine in chronic heart failure.

Methods

The SHIFT population was divided by baseline heart rate ≥75 or <75 bpm. The effect of ivabradine was analysed for primary composite endpoint (cardiovascular death or HF hospitalization) and other endpoints.

Results

In the ≥75 bpm group, ivabradine reduced primary endpoint (HR 0.76, 95 % CI 0.68–0.85, P < 0.0001), all-cause mortality (HR 0.83, 95 % CI, 0.72–0.96, P = 0.0109), cardiovascular mortality (HR 0.83, 95 % CI, (0.71–0.97, P = 0.0166), HF death (HR 0.61, 95 % CI, 0.46–0.81, P < 0.0006), and HF hospitalization (HR 0.70, 95 % CI, 0.61–0.80, P < 0.0001). Risk reduction depended on heart rate after 28 days, with the best protection for heart rates <60 bpm or reductions >10 bpm. None of the endpoints was significantly reduced in the <75 bpm group, though there were trends for risk reductions in HF death and hospitalization for heart rate <60 bpm and reductions >10 bpm. Ivabradine was tolerated similarly in both groups.

Conclusion

The effect of ivabradine on outcomes is greater in patients with heart rate ≥75 bpm with heart rates achieved <60 bpm or heart rate reductions >10 bpm predicting best risk reduction. Our findings emphasize the importance of identification of high-risk HF patients by high heart rates and their treatment with heart rate-lowering drugs such as ivabradine.     

Comparison of sustained rate control in atrial fibrillation with rapid ventricular rate: Metoprolol vs. Diltiazem

ObjectiveThe objective of this study was to compare sustained rate control with intravenous (IV) diltiazem vs. IV metoprolol in acute treatment of atrial fibrillation (AF) with rapid ventricular rate (RVR) in the emergency department (ED).MethodsThis retrospective chart review at a large, academic medical center identified patients with AF with RVR diagnosis who received IV diltiazem or IV metoprolol in the ED. The primary outcome was sustained rate control defined as heart rate (HR) < 100 beats per minute without need for rescue IV medication for 3 h following initial rate control attainment. Secondary outcomes included time to initial rate control, HR at initial control and 3 h, time to oral dose, admission rates, and safety outcomes.ResultsBetween January 1, 2016 and November 1, 2018, 51 patients met inclusion criteria (diltiazem n = 32, metoprolol n = 19). No difference in sustained rate control was found (diltiazem 87.5% vs. metoprolol 78.9%, p = 0.45). Time to rate control was significantly shorter with diltiazem compared to metoprolol (15 min vs. 30 min, respectively, p = 0.04). Neither hypotension nor bradycardia were significantly different between groups.ConclusionsChoice of rate control agent for acute management of AF with RVR did not significantly influence sustained rate control success. Safety outcomes did not differ between treatment groups.     

Optimal image reconstruction phase at low and high heart rates in dual-source CT coronary angiography

The purpose of this study was to determine the cardiac phase having the highest coronary sharpness for low and high heart rate patients scanned with dual source CT (DSCT) and to compare coronary image sharpness over different cardiac phases. DSCT coronary CT scans for 30 low heart rate (≤70 beats per minute- bpm) and 30 high heart rate (>70 bpm) patients were reconstructed into different cardiac phases, starting at 30% and increasing at 5% increments until 70%. A blinded observer graded image sharpness per coronary segment, from which sharpness scores were produced for the right (RCA), left main (LM), left anterior descending (LAD), and circumflex (Cx) coronary arteries. For each coronary artery, the phase with maximal image sharpness was identified with repeated measures analysis of variance. Comparison of coronary sharpness between low and high heart rate patients was made using generalized estimating equations. For low heart rates the highest sharpness scores for all four vessels (RCA, LM, LAD, and Cx) were at the 65 or 70% phase, which are end-diastolic cardiac phases. For high heart rates the highest sharpness scores were between the 35 and 45% phases, which are end-systolic phases. Low heart rate patients had higher coronary sharpness at most cardiac phases; however, patients with high heart rates had higher coronary sharpness in the 45% phase for all four vessels (P < 0.0001). Using DSCT scanning, optimal image sharpness is obtained in end-diastole at low heart rates and in end-systole in high heart rates.     

Heart rate outcomes with concomitant parenteral calcium channel blockers and beta blockers in rapid atrial fibrillation or flutter

BackgroundPatients who present with atrial fibrillation (AF) or flutter with rapid ventricular response (RVR) and hemodynamic stability may be managed with either an intravenous (IV) nondihydropyridine calcium channel blocker (CCB) or a beta-blocker (BB). Patients without improved heart rates may need to switch to, or add, a second AV nodal blocker.ObjectiveTo evaluate the incidence of rate control achievement and bradycardia in patients in AF or atrial flutter with RVR who receive both an intravenous CCB and a BB.MethodsA retrospective chart review of patients who received concomitant intravenous CCB or BB for the treatment of rapid AF or atrial flutter from April 2016 through July 2018 in the emergency department. Patients were excluded if the second agent was ordered but not administered, or if they received IV amiodarone or digoxin.ResultsA total of 136 patients were included in the analysis, and of those, 46% (n = 62) of patients achieved a heart rate <110 bpm without bradycardia, and 3.7% (n = 5) developed bradycardia. Age, initial heart rate, time between CCB and BB administration, addition of an oral CCB or BB administration, or administration of IV magnesium did not impact target heart rate achievement.ConclusionAdding a second nodal blocker in patients who did not achieve rate control with the first agent resulted in heart rate control 46% of the time. The development of symptomatic bradycardia was uncommon.     

Impact of a vendor-specific motion-correction algorithm on image quality,interpretability, and diagnostic performance of daily routine coronary CT angiography: influence of heart rate on the effect of motion-correction

To investigate the impact of a vendor-specific motion-correction algorithm on morphological assessment of coronary arteries using coronary CT angiography (cCTA) and to evaluate the influence of heart rate (HR) on the motion-correction effect of this algorithm. Eighty-four patients (mean age 56.3 ± 11.4 years; 53 males) were divided into two groups with a HR of ≥65 and <65 bpm during cCTA, respectively. Images were assigned quality scores (graded 1–4) on coronary segments. Interpretability was defined as a grade >1. Catheter angiography was used to determine the diagnostic accuracy of cCTA for detecting significant stenosis (≥50 %). We compared the image quality, interpretability and diagnostic accuracy between the standard and motion-correction reconstructions in both groups. The motion-correction reconstructions showed significantly (p < 0.05) higher image quality in the proximal and middle right coronary artery (RCA) in the low HR group (57.2 ± 5.0 bpm; n = 51) and proximal-to-distal RCA, posterior descending artery, and proximal and distal left circumflex artery in the high HR group (71.1 ± 4.6 bpm; n = 33). The per-segment interpretability was significantly higher using motion-correction algorithm in the middle RCA in the low HR group and in the proximal and middle RCA in high HR group. Overall, the image quality and interpretability were improved using motion-correction reconstructions in both groups (p < 0.05). Motion-correction reconstruction demonstrated higher (p < 0.05) diagnostic accuracy in 25 patients from both groups. Use of the motion-correction algorithm improves the overall image quality and interpretability of cCTA in both groups. However, it may be more beneficial to the patients with a higher HR.     

双源CT低剂量自适应扫描序列在冠状动脉成像中的应用

目的：探讨双源CT低剂量自适应扫描序列在冠状动脉成像中的应用价值。方法：将51例行双源CT冠状动脉成像的患者（心率≥65 bpm）采用自适应序列门控扫描模式,数据采集期相根据屏气时心率设定：A组24例患者（65 bpm≤心率〈75 bpm）,采集期相设为70%R-R间期,B组27例患者（心率≥75 bpm）,采集期相设为40%R-R间期。管电压根据体质量指数（BMI）调整：BMI≥25 kg/m^2,120 kV;BMI〈25 kg/m^2,100 kV。分别对两组的图像质量和辐射剂量进行评价。结果：A组共评价299段冠状动脉,B组共评价345段冠状动脉。两组可评价的冠状动脉节段评分为3-4分者分别占91.3%和92.2%;评分为1-2分者右冠状动脉（RCA）最多,其次是左回旋支（LCX）;心率波动范围3-44 bpm。A组图像质量总体平均评分为（3.53±0.73）分,B组为（3.59±0.63）分。A组总体平均有效剂量为（2.85±0.93）mSv,B组为（3.10±0.86）mSv。结论：双源CT行低剂量自适应序列门控扫描能够显著降低辐射剂量,在心率≥65 bpm的患者中也可以获得满足临床诊断的图像质量。     

Prospective versus retrospective ECG-gated 64-detector coronary CT angiography for evaluation of coronary artery bypass graft patency: comparison of image quality,radiation dose and diagnostic accuracy

We aimed to evaluate image quality, radiation dose and diagnostic accuracy of coronary CT angiography (CCTA) with a prospectively gated transverse-axial scan (PGT) compared with a retrospectively gated helical scan (RGH), using a 64-slice scanner in patients who underwent coronary artery bypass graft (CABG). Of the 131 consecutive patients that underwent CABG using 64-slice multidetector row computed tomography during 2008, patients with heart rate (HR) of <75 beats/minute (bpm), and HR variation <10 bpm were included in the study. PGT was performed on 39 patients with 93 grafts, with RGH performed on 43 patients with 102 grafts. Image quality (1: excellent—4: poor) and estimated radiation dose were compared between the two groups. Of these, a total of 64 segments in 26 patients were subjected to invasive coronary angiography (ICA) for clinical reasons. Diagnostic accuracy of CCTA for evaluation of graft was performed between the two groups with ICA as a reference standard in terms of significant stenosis (≥ 50% of luminal stenosis). The image quality was not statistically different in the two groups. Mean effective radiation dose was 6.5 mSv in PGT-group, which was significantly lower than that in the RGH-group (21.2 mSv; P < 0.001). There was no statistically significant difference in diagnostic accuracy between the two groups (PGT-group versus RGH-group; 93.1% versus 91.4%). PGT can achieve dose reductions of up to 70% compared to RGH while maintaining image quality and high diagnostic accuracy in patients undergoing CABG.     

The feasibility of halfcycle reconstruction in high heart rates in coronary CT angiography using 320-row CT

Our aim was to investigate when halfcycle reconstruction (HCR) was feasible in patients who were predicted to have a heart rate over 65 bpm in coronary CT angiography (CTA) using 320-row CT. Seventy-four patients who underwent multiple heart beat scanning were included. The time to reach 230 HU at the ascending aorta during the bolus tracking scan was recorded (T₂₃₀). HCR image and multicycle reconstruction (MCR) image were reconstructed for each patient. Image quality for each coronary segment was rated on a 3-point scale (3: good, 1: poor). For each patient, we determined that a single beat acquisition was feasible for diagnosis (HCR group) when the number of segments graded score 1 in the HCR image was the same or less than that in the MCR image. Otherwise, we included the patients in the MCR group. HCR group and MCR group included 38 and 36 patients, respectively. Regression analysis showed that body height >1.66 m (odds ratio (OR), 5.74; CI 1.59–25.6; p < 0.007), T₂₃₀ >16 s (OR 3.11; CI 1.07–9.58; p = 0.04), and heart rate ≤72 bpm (OR 3.18; CI 1.11–9.49; p = 0.03) were related with the HCR group. When all three criteria were fulfilled, the calculated probability that MCR would improve image quality was only 7 %. When the heart rate is ≤72 bpm, single heart beat acquisition is feasible for patients with body height >1.66 m and T₂₃₀ > 16 s in coronary CTA using 320-row CT.     

Failed heart rate control with oral metoprolol prior to coronary CT angiography: effect of additional intravenous metoprolol on heart rate, image quality and radiation dose

The purpose of this study was to evaluate the effect of intravenous (IV) metoprolol after a suboptimal heart rate (HR) response to oral metoprolol (75–150 mg) on HR control, image quality (IQ) and radiation dose during coronary CTA using 320-MDCT. Fifty-three consecutive patients who failed to achieve a target HR of < 60 bpm after an oral dose of metoprolol and required supplementary IV metoprolol (5–20 mg) prior to coronary CTA were evaluated. Patients with HR < 60 bpm during image acquisition were defined as responders (R) and those with HR ≥ 60 bpm as non-responders (NR). Two observers assessed IQ using a 3-point scale (1–2, diagnostic and 3, non-diagnostic). Effective dose (ED) was estimated using dose-length product and a 0.014 mSV/mGy.cm conversion factor. Baseline characteristics and HR on arrival were similar in the two groups. 58 % of patients didn’t achieve the target HR after receiving IV metoprolol (NR). R had a significantly higher HR reduction after oral (mean HR 63.9 ± 4.5 bpm vs. 69.6 ± 5.6 bpm) (p < 0.005) and IV (mean HR 55.4 ± 3.9 bpm vs. 67.4 ± 5.3 bpm) (p < 0.005) doses of metoprolol. Studies from NR showed a significantly higher ED in comparison to R (8.0 ± 2.9 vs. 6.1 ± 2.2 mSv) (p = 0.016) and a significantly higher proportion of non-diagnostic coronary segments (9.2 vs. 2.5 %) (p < 0.001). 58 % of patients who do not achieve a HR of <60 bpm prior to coronary CTA with oral fail to respond to additional IV metoprolol and have studies with higher radiation dose and worse image quality.     

Diagnostic accuracy of multislice computed tomography coronary angiography is improved at low heart rates

Purpose: Assess the effect of heart rate on diagnostic accuracy for the detection of significant coronary artery stenosis using 16-row multislice computed tomography (MSCT). Material and methods: About 120 patients (105 males; 59±11 years) with suspected coronary artery disease who underwent conventional coronary angiography (CA) and MSCT-CA were retrospectively enrolled for the study. Patients underwent a MSCT-CA (Sensation 16, Siemens, Germany), with the following protocol: collimation 16×0.75 mm, gantry rotation time 420 ms, feed/rotation 3.0 mm, kV 120, mAs 400–500. The protocol for contrast material administration was 100 ml of Iodixanol (Visipaque 320 mg l/ml, Amersham, UK) at 4 ml/s and the delay was defined with a bolus tracking technique. In all patients the mean heart rate (HR) during the scan was used as a criteria to divide the population in two groups of 60 patients each. In one group (Low HR) the 60 patients with lower heart rates, and in the other group (High HR) the patients with higher heart rates. In the two groups diagnostic accuracy (per coronary segment) for the detection of significant stenosis (≥50% lumen reduction) was evaluated in vessels ≥2 mm of diameter using quantitative CA as reference standard. The difference in diagnostic accuracy were compared with a Chi² test and a p<0.05 was considered significant. Results: There was no significant difference between the two groups regarding age, gender, weight, mean intravascular attenuation, and calcium score. Overall 1310 (652 for Low HR and 658 for High HR) segments with 219 (105 for Low HR and 114 for High HR) significant lesions were available for the analysis. The average heart rate was 52±4HU and 63±5HU for Low HR and High HR, respectively (p<0.001). The sensitivity and specificity were 92 and 96% for Low HR and 90 and 92% for High HR (p<0.05). There were 22 vs. 44 false positives, and 8 vs. 12 false negatives in the Low HR and High HR, respectively. Conclusion: Increasing HR significantly deteriorates diagnostic accuracy in MSCT-CA.     

A new method to quantify postexercise ST‐deviation – the ST‐deficit. A study in men at high and low‐risk for coronary heart disease

Background Quantitative heart rate adjusted exercise ST criteria like μV/beats per minute (bpm) improve the diagnostic accuracy of the exercise ECG. However, there are few quantitative HR adjusted postexercise variables available. The aim of the present exercise study was to evaluate a new such variable from computerized averaging of the postexercise ECG. Methods The presence of possible myocardial ischaemia in a population based sample of 74 elderly male hypertensives at high‐risk of coronary heart disease, and in 42 age‐matched clinically healthy males (reference group) at low‐risk was assessed by exercise ECG. All men had a normal resting ECG without signs of ischaemia. Variables studied: standard ST‐criteria, ST/HR slope ≤–2·4 μV · bpm^–1, shape of the rate‐recovery loop, the latter also with a new quantitative variable, the ST‐deficit. Results In spite of a normal resting ECG many subjects showed an abnormal ST/HR slope during exercise, 43% in the hypertension group and 26% in the reference group. An abnormal rate‐recovery loop (ST‐deficit) also contributed substantially to identify patients with possible myocardial ischaemia, 30 vs. 10%, respectively (P<0·02); cumulatively for the two HR adjusted criteria 53% vs. 29%, respectively (P<0·02). Mean ST‐deficit was significantly lower in the high‐risk group. Conclusions Effort‐related myocardial ischaemia is frequently silent in elderly high‐risk hypertensives and necessitates testing, preferably with computerized exercise ECG and heart rate adjusted ST criteria. A new quantitative variable to assess the postexercise rate‐recovery loop in the time domain, the ST‐deficit is described. This variable seems to effectively discriminate between subjects with low and high‐risk for coronary heart disease and thus provides new information. Further studies are warranted to validate this variable against myocardial perfusion scintigraphy and coronary angiography.