Coronary vasospasm induced during isoproterenol head-up tilt test

A contemporary review of the head-up tilt test: Utility and limitations

The Head-Up Tilt Test (HUTT) has been widely used for the past four decades as part of the overall assessment of the potential causes of collapse in patients with recurring transient loss of consciousness (TLOC) of unknown cause. The ability of a positive HUTT often to reproduce patient symptoms and illustrate to the patient that the physician is confident of the diagnosis have been major advances in clinical TLOC management. Tilt testing has been particularly important in understanding and diagnosing vasovagal syncope (VVS) and orthostatic hypotension. Despite HUTT having great clinical utility, different HUTT protocols and drug provocations result in different test yields. Limited HUTT reproducibility has led some researchers to criticize HUTT utility. As in most medical tests, limitations are part of the test. Herein, we provide a contemporary review of HUTT's utility in diagnosing and managing various TLOC disorders with intent to clarify its role in clinical practice.

Clinical Features of Patients Undergoing the Head-Up Tilt Test and Its Safety and Efficacy in Diagnosing Vasovagal Syncope in 4,873 Patients

Background: The head-up tilt test (HUTT) is a useful diagnostic tool in patients with suspected vasovagal syncope (VVS).

Objectives: We aimed to investigate the direct drug-potentiated HUTT in patients with recurrent syncope or precursor syncope and to assess the diagnostic value of the direct drug-potentiated HUTT.

Methods: The medical history and direct drug-potentiated HUTT records of patients who complained of syncope or precursor syncope and who visited The Xianyang Central Hospital from January 2016 to December 2020 were retrospectively reviewed.

Results: A total of 4,873 patients (age = 43.8 ± 17.6 years; male = 2,064 [42.4%]) were enrolled in our study. Overall, 2,343 (48.1%) showed positive responses as follows: 1,260 (25.9%) with the mixed type, 34 (0.7%) with the cardioinhibitory type, 580 (11.9%) with the vasodepressor type, 179 (3.7%) with postural tachycardia syndrome (POTS), and 290 (6.0%) with orthostatic hypotension (OH). The study showed that prior to syncope or near-syncope symptoms, patients first presented an increase in heart rate (HR), followed by decreases in blood pressure (BP) and HR successively. Among the patients in the syncope group, the sensitivity of the HUTT was 65.9%, which was significantly higher than a sensitivity of 44.8% for patients in the non-syncope group (P < 0.01). The sensitivity of the HUTT was higher for females than males in both the syncope group (52.6% in males and 77.9% in females, P < 0.01) and the non-syncope group (36.5% in males and 50.6% in females, P < 0.01). Within the four age groups (<20, 21–40, 41–60, and >60 years old), the sensitivities were 74.7%, 67.7%, 45.6%, and 31.2%, respectively. And all gender, age and symptom (whether suffered from a syncope or not) significantly affected the positive responses of HUTT. There were two adverse events and no deaths during the HUTT in this study.

Conclusion: The direct drug-potentiated HUTT is a safe and highly sensitive tool with which to diagnose VVS. Patients with precursor syncope symptoms without syncope should undergo a HUTT, especially young females presenting with weakness and sweating, which can decrease the probability of a misdiagnosis or a missed diagnosis.

Provocation of Coronary Vasospastic Angina Using an Isoproterenol Head-up Tilt Test

The goals of this study were to determine the value of the isoproterenol (ISO) head-up tilt (HUT) test in detecting coronary vasospastic angina and to investigate the possible mechanism responsible for coronary artery spasm. The ISO + HUT test was performed in 16 patients with coronary artery spasm documented by the intracoronary ergonovine provocation test. Patients’ blood pressure and heart rate were measured at baseline, during the ISO + HUT (phase I), and during HUT after discontinuation of ISO (phase II). Patients were categorized as test-positive if they developed angina with ST-segment elevation during testing. Eight patients (50%) were test-positive (5 in phase I and 3 in phase II). Between the test-positive and test-negative groups, no significant differences were noted in the changes in blood pressure throughout the test. However, there were significant differences in the changes in heart rate from supine to 2 minutes after HUT under ISO infusion (-17 ±22 vs 11 ±25 beats/minute; p=0.035). In those patients with a positive result in the phase I stage, the heart rate decreased initially after tilt-up, and then significantly increased later (from 85 ±16 to 110 ±27 beats/minute; p=0.043), when coronary vasospasm occurred. In those patients with a positive result in the phase II stage, coronary vasospasm occurred immediately after HUT, when there was an insignificant transient increase in heart rate from the supine to the HUT position (from 85 ±12 to 92 ±11 beats/minute; p=0.109). The ISO + HUT test can provoke coronary vasospasm with ST-segment elevation in 50% of the patients with coronary artery spasm, when combined with an extensional protocol of HUT after discontinuation of ISO. This study suggests that the induction of coronary artery spasm during HUT testing is associated with a rapid elevation of sympathetic activity during augmented parasympathetic activity.

Appearance of Collateral Circulation in the Absence of Total Occlusive Spastic Coronary Artery

Development of coronary collateral vessels is described in a patient with coronary artery spasm associated with ST-segment depression. The collateral vessels disappeared after spasm was relieved and the ST segment was normalized, suggesting that the collateral vessels occurred during coronary artery spasm and were localized to the perfused ischemic area to prevent transmural myocardial ischemia.

Prognostic Value of I-123 Metaiodobenzylguanidine Imaging in Vasospastic Angina Without Significant Coronary Stenosis

BACKGROUND

Myocardial imaging is widely used to detect coronary artery disease and to assess its prognosis. In vasospastic angina (VA), cardiac imaging can provide information on disease activity, which is related to cardiac events. The aim of this study was to clarify whether exercise thallium-201 imaging (Tl-SPECT) and 123I-metaiodobenzylguanidine imaging (MIBG) have prognostic value for patients with VA, but without significant coronary artery stenosis.

METHODS AND RESULTS

One hundred and 5 patients who showed acetylcholine-induced coronary spasm, normal left ventricular function and no significant stenosis (<50%) underwent both symptom-limited Tl-SPECT and MIBG within 1 month. All patients were prescribed calcium antagonist during the follow-up period (mean 4.7 years). Exercise-induced ischemia was detected by Tl-SPECT in 53 patients and multivessel coronary spasm by coronary angiography in 33 patients. During the follow-up period, 1 patient died suddenly and another died of acute myocardial infarction (MI). Two patients developed nonfatal acute MI and 7 patients underwent emergency coronary angiography because of unstable angina. According to the baseline characteristics, VA with cardiac events showed a significantly higher heart-to-mediastinum ratio (H/M ratio) and a significantly lower MIBG washout rate than those without cardiac events (p<0.03 and p<0.02, respectively). Among 8 clinical variables, including coronary risk factors, exercise parameters and exercise-induced ischemia on Tl-SPECT and the MIBG delayed H/M ratio and washout rate, univariate Cox proportional hazard regression analysis showed that the high H/M ratio and reduced washout rate of MIBG were significant predictors of future cardiac events (relative risk (RR) =4, confidence interval (CI) =1.21-13.29, p<0.02 for H/M ratio and RR 0.92, CI 0.85-0.99, p<0.02 for washout rate). However, exercise-induced ischemia did not show any statistical significance. By multivariate Cox proportional hazard regression analysis, a reduced MIBG washout rate was the only significant predictor of future cardiac events (odds ratio =0.90, CI =0.82-1.00, p<0.04).

CONCLUSION

MIBG imaging can identify high-risk patients, even among those with VA who were previously regarded as low risk. This result strongly supports the idea that cardiac sympathetic dysfunction contributes to coronary artery spasm leading to cardiac events.

Frequency of arrhythmic events during head-up tilt testing in patients with suspected neurocardiogenic syncope or presyncope

Head-up tilt testing (HUT) is a useful diagnostic tool for evaluating suspected neurocardiogenic syncope. Although arrhythmic events during HUT have been occasionally reported, their incidence in a large number of patients is unknown. We aimed to assess the incidence and clinical significance of arrhythmic events in patients with suspected neurocardiogenic syncope who underwent HUT with isoproterenol provocation. For 2,242 patients who underwent HUT, the incidence of total arrhythmic events was 31%: bradyarrhythmias 24%, premature beats 4%, and tachyarrhythmias 3%. For 547 patients who developed bradyarrhythmias during HUT, the incidence of junctional arrhythmias was 92%. For 702 arrhythmic events, the incidence of arrhythmic events during the first phase of HUT was significantly lower than the second phase (p <0.001). The incidence of arrhythmic events in patients with positive HUT responses was significantly higher than in those with negative responses (p <0.001). In patients with positive responses, bradyarrhythmias were noted in 85%, and junctional arrhythmia was the most common arrhythmic event. Of the positive responses, 353 patients (61%) had the vasodepressive type, 181 (32%) patients the mixed type, and the remaining 39 (7%) the cardioinhibitory type. Of 2,242 patients, ventricular fibrillation occurred in 1 patient (0.04%). Thus, bradyarrhythmias were the most common arrhythmic events during HUT with isoproterenol provocation. Serious ventricular tachyarrhythmia rarely occurred.

Coronary vasospasm and the regulation of coronary blood flow

Under physiologic conditions, epicardial arteries contribute minimally to coronary vascular resistance. However, in the presence of endothelial dysfunction, stimuli that normally produce vasodilation may instead cause constriction. Examples include neural release of acetylcholine or norepinephrine, platelet activation and production of serotonin and thrombin, and release of local factors such as bradykinin. This shift from a primary endothelial-mediated vasodilator influence to one of endothelial dysfunction and unchecked vasoconstriction is precisely the milieu in which coronary vasospasm is observed. This condition, which typically occurs during periods of relatively sedentary activity, is associated with focal and transient obstruction of an epicardial arterial segment resulting in characteristic echocardiographic changes and symptoms of myocardial ischemia. This review highlights the current understanding of mechanisms regulating the coronary circulation during health and examines the pathophysiologic changes that occur with coronary spasm. Genetic and other predisposing conditions are addressed, as well as novel therapies based on recent mechanistic insights of the coronary contractile dysfunction associated with coronary spasm.

Cardiopulmonary resuscitation during coronary vasospasm induced by tilt table testing

A 65-year-old man presented to our institution with recurrent episodes of early morning chest discomfort and near syncope. An ergonovine provocation test documented a diagnosis of coronary vasospastic angina. Using our investigation of the syncope, a head-up tilt table test provoked a severe episode of coronary vasospasm that resulted in a life-threatening cardiac event. The present case reminds us that an elevation of ST segments on the electrocardiogram during tilt testing should be promptly managed as an attack of coronary vasospasm.

Usefulness of head-up tilt test in the evaluation and management of unexplained syncope or pre-syncope

This study included 87 consecutive patients with unexplained syncope or pre-syncope who had undergone the head-up tilt (HUT) test with concomitant isoproterenol infusion. A positive response was defined as development of syncope or pre-syncope in association with substantial hypotension (decline of systolic blood pressure > or = 20 mmHg). Coronary artery spasm was suggested from the clinical symptoms and electrocardiographic findings in 1 patient (1/87= 1.1%). Intolerance to isoproterenol infusion was noted in 8 cases (8/87 = 9%). Of the 78 patients who completed the study, 73 showed positive responses (73/78 = 94%). (baseline systolic blood pressure = 125 +/- 23 mmHg endpoint systolic blood pressure = 76 +/- 11 mmHg, p < 0.05; baseline heart rate = 73 +/- 14 beats per minute vs endpoint HR = 80 +/- 24 beats per minute, p < 0.05). In 73 patients who showed positive responses, the systolic blood pressure (SBP) and heart rate (HR) returned to a safe level at 2 minutes when the patients were returned to a supine position (post-study 2 minutes SBP = 124 +/- 18 mmHg vs baseline SBP 125 +/- 23 mmHg, p = NS; post-study 2 minutes HR = 82 +/- 18 beats per minute vs baseline HR = 73 +/- 14 beats per minute, p < 0.05). All 73 patients with a positive HUT test received Atenolol therapy (50 mg daily). Only 35 of these 73 patients took Atenolol regularly and had a repeat HUT test. After atenolol therapy, persistent positive responses were observed in 19 cases (19/35 = 54%) and negative responses were noted in 16 cases (16/35 = 46%). The mean dosage of isoproterenol needed to provoke a positive HUT test in 19 patients who had received Atenolol therapy and had a positive repeat HUT test was 2.3 +/- 1.2 microg/min at baseline and 3.5 +/- 0.9 microg/min for post-Atenolol therapy (p < 0.001). Sixteen patients with a negative repeat HUT test were treated continuously with Atenolol and followed for a mean period of 13 +/- 11 months (range, 1-34 months). All 16 patients were free of syncope or pre-syncope during the period of follow up. In conclusion, the HUT test is mostly well tolerated and safe, even though the test has a low rate of adverse effects. Atenolol is effective for the prevention of provoked or spontaneous recurrent syncope or pre-syncope.

Diagnostic value of dobutamine echocardiography in patients with angina-like symptoms preceding syncope

Dobutamine echocardiography was performed in 55 patients with syncope which was clinically suspected to be angina-related. We evaluated the value of using a single test, dobutamine echocardiography, in differentiating real ischemia-related from vasovagal syncope which was diagnosed by a tilt test. During testing, supraventricular arrhythmia was provoked in four (7.2%) patients. Dobutamine echocardiography identified all of six (10.9%) patients (sensitivity 100%), who were found with significant coronary stenosis by coronary angiograms. The etiology of syncope in the remaining 45 patients was investigated further by tilt testing, the findings of hypotension and bradycardia during which were compared head to head with those of dobutamine echocardiography. Tilt testing diagnosed vasovagal syncope in 31 patients, in whom only 19 (61.3%) patients developed vasovagal reflex during dobutamine echocardiography. Conclusively, dobutamine echocardiography had a high sensitivity in identifying syncope related to myocardial ischemia in patients with coronary stenosis, but a low sensitivity (61.3%), high specificity (90.5%) and high positive predictive value (81.8%) in detecting the syncope patients with angina caused by vasovagal effect.