Variability of episodic ST segment depression in chronic stable angina: implications for individual and group trials of therapeutic efficacy

Dynamic detection and reversal of myocardial ischemia using an artificially intelligent bioelectronic medicine

Myocardial ischemia is spontaneous, frequently asymptomatic, and contributes to fatal cardiovascular consequences. Importantly, myocardial sensory networks cannot reliably detect and correct myocardial ischemia on their own. Here, we demonstrate an artificially intelligent and responsive bioelectronic medicine, where an artificial neural network (ANN) supplements myocardial sensory networks, enabling reliable detection and correction of myocardial ischemia. ANNs were first trained to decode spontaneous cardiovascular stress and myocardial ischemia with an overall accuracy of ~92%. ANN-controlled vagus nerve stimulation (VNS) significantly mitigated major physiological features of myocardial ischemia, including ST depression and arrhythmias. In contrast, open-loop VNS or ANN-controlled VNS following a caudal vagotomy essentially failed to reverse cardiovascular pathophysiology. Last, variants of ANNs were used to meet clinically relevant needs, including interpretable visualizations and unsupervised detection of emerging cardiovascular stress. Overall, these preclinical results suggest that ANNs can potentially supplement deficient myocardial sensory networks via an artificially intelligent bioelectronic medicine system.

Myocardial Ischemia Induced by 5-Fluorouracil: A Prospective Electrocardiographic and Cardiac Biomarker Study

BACKGROUND

Cardiotoxicity induced by 5-fluorouracil (5-FU) is well known but poorly understood. In this study, we undertook ECG recording (Holter) and analyses of the biomarkers troponin and copeptin in patients receiving 5-FU to increase our understanding of the cardiotoxicity.

SUBJECTS, MATERIALS, AND METHODS

Patients with colorectal or anal cancer that received first-time treatment with 5-FU-based chemotherapy were prospectively included. Holter recording, clinical evaluation, 12-lead electrocardiogram, and assessment of plasma concentrations of troponin I and copeptin were performed before (control) and during 5-FU treatment (intervention).

RESULTS

A total of 108 patients were included, 82 with colorectal and 26 with anal cancer. The proportion of patients with myocardial ischemia on Holter recording was significantly higher during the first 5-FU infusion (14.1%) than before (3.7%; p = .001). The ischemic burden per day (p = .001), the number of ST depression episodes per day (p = .003), and the total duration of ischemic episodes per day (p = .003) were higher during the first 5-FU infusion than before, as was plasma copeptin (p < .001), whereas plasma troponin I was similar (p > 0.999). Six patients (5.6%) developed acute coronary syndromes and two (1.8%) developed symptomatic arrhythmias during 5-FU treatment.

CONCLUSION

5-FU infusion is associated with an increase in the number of patients with myocardial ischemia on Holter recording. According to biomarker analyses, 5-FU is associated with an increase in copeptin, but rarely with increases in cardiac troponin I. However, 5%-6% of the patients developed acute coronary syndromes during treatment with 5-FU.

IMPLICATIONS FOR PRACTICE

Symptomatic 5-fluorouracil (5-FU) cardiotoxicity occurs in 0.6%-19% of patients treated with this drug, but a small electrocardiographic (Holter) study has revealed silent myocardial ischemia in asymptomatic patients, suggesting a more prevalent subclinical cardiac influence. This study demonstrated a significant increase in the number of patients with myocardial ischemia on Holter recording during 5-FU treatment and an increase in ischemic burden. Cardiac biomarker analyses suggested that 5-FU infusion results in endogenous stress (increased copeptin) but rarely induces myocyte injury (no change in troponin). These findings suggest a more prevalent cardiac influence from 5-FU and that Holter recording is an important tool in the evaluation of patients with suspected cardiotoxicity from 5-FU.

A Novel Point-of-Care Smartphone Based System for Monitoring the Cardiac and Respiratory Systems

Cardio-respiratory monitoring is one of the most demanding areas in the rapidly growing, mobile-device, based health care delivery. We developed a 12-lead smartphone-based electrocardiogram (ECG) acquisition and monitoring system (called “cvrPhone”), and an application to assess underlying ischemia, and estimate the respiration rate (RR) and tidal volume (TV) from analysis of electrocardiographic (ECG) signals only. During in-vivo swine studies (n = 6), 12-lead ECG signals were recorded at baseline and following coronary artery occlusion. Ischemic indices calculated from each lead showed statistically significant (p < 0.05) increase within 2 min of occlusion compared to baseline. Following myocardial infarction, spontaneous ventricular tachycardia episodes (n = 3) were preceded by significant (p < 0.05) increase of the ischemic index ~1–4 min prior to the onset of the tachy-arrhythmias. In order to assess the respiratory status during apnea, the mechanical ventilator was paused for up to 2 min during normal breathing. We observed that the RR and TV estimation algorithms detected apnea within 7.9 ± 1.1 sec and 5.5 ± 2.2 sec, respectively, while the estimated RR and TV values were 0 breaths/min and less than 100 ml, respectively. In conclusion, the cvrPhone can be used to detect myocardial ischemia and periods of respiratory apnea using a readily available mobile platform.

Effects of Intensive Versus Moderate Lipid-Lowering Therapy on Myocardial Ischemia in Older Patients With Coronary Heart Disease

Background— Clinical trials have demonstrated that, compared with placebo, intensive statin therapy reduces ischemia in patients with acute coronary syndromes and in patients with stable coronary artery disease. However, no studies to date have assessed intensive versus moderate statin therapy in older patients with stable coronary syndromes.

Methods and Results— A total of 893 ambulatory coronary artery disease patients (30% women) 65 to 85 years of age with ≥1 episode of myocardial ischemia that lasted ≥3 minutes during 48-hour ambulatory ECG at screening were randomized to atorvastatin 80 mg/d or pravastatin 40 mg/d and followed up for 12 months. The primary efficacy parameter (absolute change from baseline in total duration of ischemia at month 12) was significantly reduced in both groups at month 3 and month 12 (both P <0.001 for each treatment group) with no significant difference between the treatment groups. Atorvastatin-treated patients experienced greater low-density lipoprotein cholesterol reductions than did pravastatin-treated patients, a trend toward fewer major acute cardiovascular events (hazard ratio, 0.71; 95% confidence interval, 0.46, 1.09; P =0.114), and a significantly greater reduction in all-cause death (hazard ratio, 0.33; 95% confidence interval, 0.13, 0.83; P =0.014).

Conclusions— Compared with moderate pravastatin therapy, intensive atorvastatin therapy was associated with reductions in cholesterol, major acute cardiovascular events, and death in addition to the reductions in ischemia observed with both therapies. The contrast between the therapies’ differing efficacy for major acute cardiovascular events and death and their nonsignificant difference in efficacy for reduction of ischemia suggests that low-density lipoprotein cholesterol–lowering thresholds for ischemia and major acute cardiovascular events may differ. The Study Assessing Goals in the Elderly (SAGE) demonstrates that older men and women with coronary artery disease benefit from intensive statin therapy.

Effect of Intensive Lipid Lowering, With or Without Antioxidant Vitamins, Compared With Moderate Lipid Lowering on Myocardial Ischemia in Patients With Stable Coronary Artery Disease

Background— Lipid lowering with statins prevents adverse cardiac events. Both lipid-lowering and antioxidant therapies may favorably affect vasomotor function and thereby improve ischemia.

Methods and Results— In a randomized, double-blind, placebo-controlled trial, 300 patients with stable coronary disease, a positive exercise treadmill test, 48-hour ambulatory ECG with ≥1 episode of ischemia, and fasting total cholesterol of 180 to 250 mg/dL were assigned to 1-year treatment with intensive atorvastatin to reduce LDL to <80 mg/dL (n=96), intensive atorvastatin to reduce LDL to <80 mg/dL plus antioxidant vitamins C (1000 mg/d) and E (800 mg/d) (n=101), or diet and low-dose lovastatin, if needed, to reduce LDL to <130 mg/dL (n=103; control group). Ischemia end points, including ambulatory ECG monitoring and exercise treadmill testing, and endothelial assessment using brachial artery flow-mediated dilation were obtained at baseline and at 6 and 12 months. Baseline characteristics were similar in all groups. LDL decreased from ≈153 mg/dL at baseline in the 2 atorvastatin groups to ≈83 mg/dL at 12 months (each P <0.0001) and from 147 to 120 mg/dL in the control group ( P <0.0001). During ambulatory ECG monitoring, mean number of ischemic episodes per 48 hours decreased 31% to 61% in each group (each P <0.001; P =0.15 across groups), without a change in daily heart rate activity. Mean duration of ischemia for 48 hours decreased 26% to 62% in each group (each P <0.001; P =0.06 across groups). Mean exercise duration to 1-mm ST-segment depression significantly increased in each group, but total exercise duration and mean sum of maximum ST depression were unchanged. Angina frequency decreased in each group. There was no incremental effect of supplemental vitamins C and E on any ischemia outcome. Flow-mediated dilation studies indicated no meaningful changes.

Conclusions— Intensive lipid lowering with atorvastatin to an LDL level of 80 mg/dL, with or without antioxidant vitamins, does not provide any further benefits in ambulatory ischemia, exercise time to onset of ischemia, and angina frequency than moderate lipid lowering with diet and low-dose lovastatin to an LDL level of <120 mg/dL.

The safety and effectiveness of esmolol in the perioperative period in patients undergoing abdominal aortic surgery

OBJECTIVES

To determine (1) if perioperative use of esmolol in major vascular surgery patients provides strict heart rate (HR) control, (2) what doses of esmolol are required to do this, and (3) does this control influence myocardial ischemia or result in adverse consequences.

DESIGN

Prospective study of 40 patients randomized to two groups: The HR was controlled to either less than 80 beats/min (group 80) or less than 110 beats/min (group 110) using esmolol. Patients were monitored continuously for electrocardiographic changes perioperatively. HR control began after induction of anesthesia and continued for 48 hours thereafter.

SETTING

Operating room and intensive care unit.

PATIENTS

Patients undergoing abdominal vascular surgery involving aortic cross-clamping.

INTERVENTIONS

Esmolol was titrated until the target HR was met.

MEASUREMENTS AND RESULTS

Only one patient demonstrated an adverse effect. The median infusion rates were 100 and 12.5 microg/kg/min for groups 80 and 110. Target HR was met less in group 80 than in group 110, primarily in the postoperative period. Ischemia patterns were not significantly different between groups.

CONCLUSION

Using esmolol for HR control in the intraoperative period for abdominal vascular surgery patients is effective and safe. HR control was much less effective in the postoperative period, but esmolol is safe when used at recommended doses. Further study with a larger number of patients is necessary to determine whether strict HR control with esmolol affects the incidence of myocardial ischemia or infarction in this patient population.

Natural variability of transient myocardial ischaemia during daily life: an obstacle when assessing efficacy of anti-ischaemic agents?

OBJECTIVE

To assess the degree of variability of transient myocardial ischaemia during daily life in patients with coronary artery disease, which could confound the interpretation of trials of the therapeutic effects of anti-ischaemic agents.

DESIGN

Prospective method evaluation.

SETTING

Tertiary referral centre, outpatient clinic.

PATIENTS

Patients with stable angina, confirmed coronary artery disease, and a positive treadmill exercise test for ischaemia. Patients were not preselected on the basis of prior documented transient ischaemia during ambulatory ST segment monitoring.

INTERVENTIONS

A simulated drug-study with 4 monitoring phases in 16 subjects. To minimise variability in ischaemic activity, patients underwent weekly 48 hour ambulatory ST segment monitoring outside hospital off all prophylactic therapy on the same weekdays for 4 weeks.

MAIN OUTCOME MEASURE

Variability in the frequency and duration of transient myocardial ischaemia.

RESULTS

There was marked variability in both ischaemic activity and mean duration of ischaemia in patients with confirmed ischaemia, the greatest degree of variability being between patients and from day to day within weeks within patients, with a further contribution to variability being noted between fortnights within patients.

CONCLUSIONS

Despite assessment off all therapy and an adequate period of monitoring (48 hours) with small intervals between monitoring periods (5 days), marked variability in ischaemic activity was noted, and regression towards the mean was clearly shown. Ambulatory ST segment monitoring outside hospital is not a reliable method for assessing the therapeutic effects of anti-ischaemic agents.

Optimal lead selection for detection of ST segment shifts

A comparison was made to determine the ability of optimal sets of 2-6 unipolar leads and a normal Holter lead set to estimate ST potential distributions changes induced by balloon inflation during angioplasty. The performance of these lead sets was compared to measurements observed in recorded 32-lead body surface maps. Unipolar lead potentials were estimated using a linear, least mean squared error estimator of the total body surface map. The correlation between maximum ST potential change in the body surface map and that predicted by the unipolar lead sets ranged from 0.84-0.93. The correlation between maximum ST segment change measured from the body surface map and measured from the Holter leads was 0.29. Therefore, shifts in ST segment potentials can accurately be estimated from a small number of unipolar leads. In contrast, current bipolar ambulatory recording techniques may introduce significant bias to such estimates.