Radionuclide imaging of cardiac autonomic innervation

Cardiac autonomic function plays a crucial role in health and disease, with abnormalities both reflecting the severity of the disease and contributing specifically to clinical deterioration and poor prognosis. Radiotracer analogs of the sympathetic mediator norepinephrine have been investigated extensively, and are at the brink of potential widespread clinical use. The most widely studied SPECT tracer, I-123 metaiodobenzylguanidine (¹²³I-mIBG) has consistently shown a strong, independent ability to risk stratify patients with advanced congestive heart failure. Increased global cardiac uptake appears to have a high negative predictive value in terms of cardiac events, especially death and arrhythmias, and therefore and may have a role in guiding therapy, particularly by helping to better select patients unresponsive to conventional medical therapies who would benefit from device therapies such as an ICD (implantable cardioverter defibrillator), CRT (cardiac resynchronization therapy), LVAD (left ventricular assist device), or cardiac transplantation. Cardiac autonomic imaging with SPECT and PET tracers also shows potential to assess patients following cardiac transplant, those with primary arrhythmic condition, coronary artery disease, diabetes mellitus, and during cardiotoxic chemotherapy. Radiotracer imaging of cardiac autonomic function allows visualization and quantitative measurements of underlying molecular aspects of cardiac disease, and should therefore provide a perspective that other cardiac tests cannot.     

Cardiac autonomic imaging with SPECT tracers

Radionuclide cardiac imaging has potential to assess underlying molecular, electrophysiologic, and pathophysiologic processes of cardiac disease. An area of current interest is cardiac autonomic innervation imaging with a radiotracer such as ¹²³I-meta-iodobenzylguanidine (¹²³I-mIBG), a norepinephrine analogue. Cardiac ¹²³I-mIBG uptake can be assessed by planar and SPECT techniques, involving determination of global uptake by a heart-to-mediastinal ratio, tracer washout between early and delayed images, and focal defects on tomographic images. Cardiac ¹²³I-mIBG findings have consistently been shown to correlate strongly with heart failure severity, pre-disposition to cardiac arrhythmias, and poor prognosis independent of conventional clinical, laboratory, and image parameters. ¹²³I-mIBG imaging promises to help monitor a patient’s clinical course and response to therapy, showing potential to help select patients for an ICD and other advanced therapies better than current methods. Autonomic imaging also appears to help diagnose ischemic heart disease and identify higher risk, as well as risk-stratify patients with diabetes. Although more investigations in larger populations are needed to strengthen prior findings and influence modifications of clinical guidelines, cardiac ¹²³I-mIBG imaging shows promise as an emerging technique for recognizing and following potentially life-threatening conditions, as well as improving our understanding of the pathophysiology of various diseases.     

123I-mIBG Scintigraphy to predict risk for adverse cardiac outcomes in heart failure patients: Design of two prospective multicenter international trials

Background  ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) consists of two identical prospective open-label, multicenter, phase 3 studies (MBG311 and MBG312) evaluating the prognostic usefulness of ¹²³I-mIBG scintigraphy for identifying subjects with heart failure who will experience a major adverse cardiac event. Methods  Subjects with NYHA class II and III heart failure and left ventricular ejection fraction ≤35% were eligible for the trials. Subjects underwent planar and SPECT ¹²³I-mIBG myocardial imaging, as well as echocardiography and gated SPECT ^99mTc-tetrofosmin myocardial perfusion imaging. Subjects are then monitored on a regular basis for 2 years. Time to first occurrence of one of the following—NYHA class progression; potentially life-threatening arrhythmic event (including ICD discharge); or cardiac death, as verified by an independent adjudication panel—will be analyzed in comparison to quantitative parameters derived from ¹²³I-mIBG imaging. The primary efficacy analysis will employ the heart/mediastinum ratio on 4-hour delayed planar imaging, while secondary efficacy analyses will examine quantitative results from both planar and SPECT ¹²³I-mIBG images, as well as from ^99mTc-tetrofosmin SPECT and echocardiography. Conclusion  The results of the ADMIRE-HF trials will provide prospective validation of the potential role of ¹²³I-mIBG scintigraphy in assessing prognosis and developing management strategies for patients with heart failure. Funding Source: GE Healthcare.     

I-123-<Emphasis Type="Italic">m</Emphasis>IBG myocardial imaging for assessment of risk for a major cardiac event in heart failure patients: insights from a retrospective European multicenter study

Purpose Single-center experiences have shown that myocardial meta-iodobenzylguanidine (mIBG) uptake has prognostic value in heart failure (HF) patients. To verify these observations using a rigorous clinical trial methodology, a retrospective review and prospective quantitative reanalysis was performed on a series of cardiac ¹²³I-mIBG scans acquired during a 10-year period at six centers in Europe. Methods ¹²³I-mIBG scans obtained on 290 HF patients [(262 with left ventricular ejection fraction (LVEF) < 50%)] from 1993 to 2002 were reanalyzed using a standardized methodology to determine the heart-to-mediastinum ratio (H/M) on delayed planar images. All image results were verified by three independent reviewers. Major cardiac events [MCEs; cardiac death, cardiac transplant, potentially fatal arrhythmia (including implantable cardioverter-defibrillator discharge)] during 24-month follow-up were confirmed by an adjudication committee. Results MCEs occurred in 67 patients (26%): mean H/M ratio was 1.51 ± 0.30 for the MCE group and 1.97 ± 0.54 for the non-MCE group (p < 0.001). Two-year event-free survival using an optimum H/M ratio threshold of 1.75 was 62% for H/M ratio less than 1.75, 95% for H/M ratio greater than or equal to 1.75 (p < 0.0001). Logistic regression showed H/M ratio and LVEF as the only significant predictors of MCE. Using the lower and upper H/M quartiles of 1.45 and 2.17 as high- and very low-risk thresholds, 2-year event-free survival rates were 52% and 98%, respectively. Among patients with LVEF ≤ 35% and H/M ≥ 1.75 (n = 73), there were nine MCEs because of progressive HF and only one because of an arrhythmia. Conclusion Application of a clinical trial methodology via the retrospective reanalysis of ¹²³I-mIBG images confirms the previously reported prognostic value of this method in HF patients, including potential identification of a quantitative threshold for low risk for cardiac mortality and potentially fatal ventricular arrhythmias.     

The utility of ADMIRE-HF risk score in predicting serious arrhythmic events in heart failure patients: Incremental prognostic benefit of cardiac 123I-mIBG scintigraphy

Background

A minority of heart failure (HF) patients who undergo implantable cardioverter defibrillator (ICD) implantation for primary prevention of sudden cardiac death (SCD) receive device therapy. Whether the addition of mIBG scintigraphy to conventional markers of arrhythmic risk can provide incremental risk stratification in HF patients has not been investigated.

Methods

We identified 778 patients from the ADMIRE-HF study with LVEF < 35% and class II or III HF symptoms who did not have an ICD at the time of enrollment. Patients were followed up prospectively (median = 17 months) for occurrence of arrhythmic events (ArE). Heart-to-mediastinum ratio (HMR) was determined as a measure of relative myocardial sympathetic nerve activity at baseline using ¹²³I-mIBG. The primary endpoint was the first occurrence of ArE: a composite of SCD, appropriate ICD therapy, resuscitated cardiac arrest or sustained ventricular tachycardia. Multivariate regression was used to determine independent predictors of ArE and to derive a risk score for ArE prediction. The score was used to group patients according to their risk for ArE. Integrated discrimination improvement (IDI) was used to quantify improvement in risk assessment with addition of HMR.

Results

ArE occurred in 54 patients (6.9%). ArE predictors were: HMR < 1.6 (HR 3.5, 95% CI [1.52-8], P = .02), LVEF < 25% (HR 2.0, 95% CI [1.28-3.05], P = .04) and SBP < 120 (HR 1.2, 95% CI [1.03-1.39], P = .02). Event rates in the low-, intermediate-, and high risk groups were 2, 10 and 16%, respectively (P = .001). The score significantly improved risk prediction (IDI = 45%, P 0.03).

Conclusion

¹²³I-mIBG significantly provides incremental risk stratification for ArE in HF patients.     

Cardiac autonomic neuropathy in patients with diabetes and no symptoms of coronary artery disease: comparison of 123I-metaiodobenzylguanidine myocardial scintigraphy and heart rate variability

Purpose

The purpose of this study was to evaluate the prevalence of cardiac autonomic neuropathy (CAN) in a cohort of patients with type 2 diabetes, truly asymptomatic for coronary artery disease (CAD), using heart rate variability (HRV) and ¹²³I-metaiodobenzylguanidine (¹²³I-mIBG) myocardial scintigraphy.

Methods

The study group comprised 88 patients with type 2 diabetes prospectively recruited from an outpatient diabetes clinic. In all patients myocardial perfusion scintigraphy, CAN by HRV and ¹²³I-mIBG myocardial scintigraphy were performed. Two or more abnormal tests were defined as CAN-positive (ECG-based CAN) and one or fewer as CAN-negative. CAN assessed by ¹²³I-mIBG scintigraphy was defined as abnormal if the heart-to-mediastinum ratio was <1.8, the washout rate was >25%, or the total defect score was >13.

Results

The prevalence of CAN in patients asymptomatic for CAD with type 2 diabetes and normal myocardial perfusion assessed by HRV and ¹²³I-mIBG scintigraphy was respectively, 27% and 58%. Furthermore, in almost half of patients with normal HRV, ¹²³I-mIBG scintigraphy showed CAN.

Conclusion

The current study revealed a high prevalence of CAN in patients with type 2 diabetes. Secondly, disagreement between HRV and ¹²³I-mIBG scintigraphy for the assessment of CAN was observed.     

Molecular imaging to predict ventricular arrhythmia in heart failure

Ventricular tachycardia (VT) is a major cause of sudden cardiac death (SCD) in patients with heart failure (HF). Left ventricular ejection fraction (LVEF) and heart failure class according to the New York Heart association (NYHA) are in most common use to identify patients that may benefit from implantable cardioverter defibrillator (ICD) therapy. But during 3 years of follow up only 35% of patients receive appropriate ICD action. Therefore, there is a continued need for refinement of selection criteria for ICD implantation. In this regard, molecular imaging of the autonomic nervous system, which plays a central role in HF progression and cardiac electro-mechanical regulation, can make a substantial contribution. This article reviews the currently available literature concerning the value of molecular neuronal cardiac imaging for prediction of ventricular arrhythmias in HF patients.     

Impact of age on myocardial uptake of 123I-mIBG in older adult subjects without coronary heart disease

Background

The purpose of this study was to examine the relationship between myocardial uptake of ¹²³I-mIBG and age in older normal adult subjects.

Methods

94 subjects (age 29-82, mean 58.5) without coronary heart disease were studied. All subjects underwent early and delayed planar and 4-hour SPECT ¹²³I-mIBG imaging. ¹²³I-mIBG uptake was quantified as heart/mediastinum ratio on planar images (H/M _p) and on SPECT images (H/M _s) reconstructed by filtered backprojection, ordered subsets-expectation maximization (OSEM), and OSEM with compensation for collimator septal penetration (DSP). Relationships between age and ¹²³I-mIBG uptake were examined by correlation analysis, t-tests, and analysis of variance.

Results

There was no significant correlation between age and H/M _p, reflecting comparable increases in activity in the two regions of interest with age. Results on SPECT analyses were comparable, with no significant correlation between age and H/M _s. Using DSP, ¹²³I-mIBG H/M _s was significantly higher in subjects ≥70 of age compared with younger subjects.

Conclusions

Both cardiac and background uptake of ¹²³I-mIBG increase with age in older subjects without coronary heart disease, resulting in stability of H/M results (planar and SPECT). This study suggests that prognostic analyses of quantitative ¹²³I-mIBG uptake in patients with heart disease do not require adjustment for patient age.     

The relationship of left ventricular mechanical dyssynchrony and cardiac sympathetic denervation to potential sudden cardiac death events in systolic heart failure

Background

Patients with heart failure (HF) are at increased risk for left ventricular (LV) dyssynchrony which is associated with sudden cardiac death (SCD). This study examined the association of LV mechanical dyssynchrony and cardiac sympathetic denervation with potential SCD events in symptomatic patients with HF and reduced ejection fraction (HFrEF).

Methods

Of the 917 HFrEF patients in ADMIRE-HF, 92 experienced adjudicated potential SCD events during a 17 months median follow-up. Propensity scores were used to assemble a matched cohort of 85 pairs of patients with and without potential SCD events. ADMIRE-HF subjects had rest gated SPECT Tc-99m and I-123 MIBG imaging. Perfusion images were processed using phase analysis software to derive phase standard deviation (SD), an index of mechanical dyssynchrony.

Results

Of the 92 patients who experienced adjudicated potential SCD events 23 had SCD, 5 fatal myocardial infarction, 7 resuscitated cardiac arrest, 46 had appropriate ICD therapy, and 11 had sustained ventricular tachycardia. Patients who experienced potential SCD events had significantly wider phase SD than matched control patients (62.3 ± 2.4º vs 55.5 ± 2.3º, P = .03) and were more likely to have a phase SD ≥ 60º (53 % vs 35 %, P = .03). Fewer patients with potential SCD events (6 % vs 15 % of the controls, P = .08) had an MIBG heart/mediastinum uptake-ratio ≥1.6.

Conclusions

Among symptomatic HFrEF patients, LV mechanical dyssynchrony is independently associated with potential SCD events. Phase analysis may provide incremental prognostic information on top of current indicators of SCD risk in HFrEF.     

Predicting the need for an implantable cardioverter defibrillator using cardiac metaiodobenzylguanidine activity together with plasma natriuretic peptide concentration or left ventricular function.

Despite widespread use of implantable cardioverter defibrillators (ICDs), their cost and the fact that only a certain group of patients fully benefits from the devices require appropriate risk stratification of patients. This study investigated whether altered cardiac autonomic function is associated with the occurrence of ICD discharge or lethal cardiac events. METHODS: Fifty-four ICD-treated patients were prospectively followed after assessment of cardiac metaiodobenzylguanidine (MIBG) activity, quantified as the heart-to-mediastinum ratio (HMR), plasma concentration of brain natriuretic peptide (BNP), and left ventricular ejection fraction (LVEF). Patients were divided into 2 groups based on the presence (group A, n = 21) or absence (group B, n = 33) of appropriate ICD discharge during a 15-mo period. RESULTS: Group A had a significantly lower level of MIBG activity and a higher plasma BNP level than did group B. Univariate analysis revealed BNP level, any medication, and late HMR to be significant predictors, and multivariate analysis showed late HMR to be an independent predictor. An HMR of less than 1.95 with a plasma BNP level of more than 187 pg/mL or an LVEF of less than 50% had significantly increased power to predict ICD shock: positive predictive values, 82% (HMR + BNP) and 58% (HMR + LVEF); negative predictive values, 73% (HMR + BNP) and 77% (HMR + LVEF); sensitivities, 45% (HMR + BNP) and 67% (HMR + LVEF); and specificities, 94% (HMR + BNP) and 70% (HMR + LVEF). CONCLUSION: When combined with plasma BNP concentration or cardiac function, cardiac MIBG activity is closely related to lethal cardiac events and can be used to identify patients who would benefit most from an ICD.     

Cardiac applications of 123I-mIBG imaging

Cardiac autonomic innervation plays a key role in maintaining hemodynamic and electrophysiologic harmony. Cardiac sympathetic function is adversely altered in many disease states, such as congestive heart failure, myocardial ischemia, and diabetes. (123)I-mIBG, a sympathetic neurotransmitter radionuclide analog, aids in the detection of sympathetic innervation abnormalities and can be imaged with planar and single-photon emission computed tomographic techniques. Cardiac (123)I-mIBG uptake can be assessed by the heart mediastinal ratio (H/M), tracer washout rate, and focal uptake defects. These parameters have been widely studied and shown to correlate strongly and independently with congestive heart failure progression, cardiac arrhythmias, cardiac death, and all-cause mortality. There is accumulating evidence that (123)I-mIBG imaging can help to monitor a patient's clinical course and response to therapy. The ability to predict potentially lethal ventricular arrhythmias promises to help more accurately select patients for implantable cardioverter defibrillators, limiting unnecessary devices and identifying additional patients at risk who do not meet current guidelines. (123)I-mIBG shows potential to help determine whether greater risk and usually more expensive ventricular assist device therapies or cardiac transplantation might be needed. Although more investigation in larger populations is needed to strengthen previous findings, cardiac (123)I-mIBG imaging shows promise as a new technique for recognizing and following potentially life-threatening cardiac conditions.     

Impact of aging on cardiac sympathetic innervation measured by <Superscript>123</Superscript>I-mIBG imaging in patients with systolic heart failure

Purpose

Sympathetic nervous system (SNS) hyperactivity is a salient characteristic of chronic heart failure (HF) and contributes to the progression of the disease. Iodine-123 meta-iodobenzylguanidine (¹²³I-mIBG) imaging has been successfully used to assess cardiac SNS activity in HF patients and to predict prognosis. Importantly, SNS hyperactivity characterizes also physiological ageing, and there is conflicting evidence on cardiac ¹²³I-mIBG uptake in healthy elderly subjects compared to adults. However, little data are available on the impact of ageing on cardiac sympathetic nerve activity assessed by ¹²³I-mIBG scintigraphy, in patients with HF.

Methods and results

We studied 180 HF patients (age?=?66.1?±?10.5 years [yrs]), left ventricular ejection fraction (LVEF?=?30.6?±?6.3 %) undergoing cardiac ¹²³I-mIBG imaging. Early and late heart to mediastinum (H/M) ratios and washout rate were calculated in all patients. Demographic, clinical, and echocardiographic data were also collected. Our study population consisted of 53 patients aged >75 years (age?=?77.7?±?4.0 year), 67 patients aged 62–72 years (age?=?67.9?±?3.2 years) and 60 patients aged ≤61 year (age?=?53.9?±?5.6 years). In elderly patients, both early and late H/M ratios were significantly lower compared to younger patients (p?<?0.05). By multivariate analysis, H/M ratios (both early and late) and washout rate were significantly correlated with LVEF and age.

Conclusions

Our data indicate that, in a population of HF patients, there is an independent age-related effect on cardiac SNS innervation assessed by ¹²³I-mIBG imaging. This finding suggests that cardiac ¹²³I-mIBG uptake in patients with HF might be affected by patient age.

     

Assessment of underlying etiology and cardiac sympathetic innervation to identify patients at high risk of cardiac death.

Cardiac (123)I-labeled metaiodobenzylguanidine (MIBG) activity has significant incremental prognostic value, but the difference between the long-term prognostic value of MIBG imaging for ischemic cardiomyopathies and the long-term prognostic value of MIBG imaging for idiopathic cardiomyopathies is not clear. This study aimed to determine whether assessment of cardiac (123)I-MIBG activities in ischemic and idiopathic cardiomyopathies have equally prognostic values and whether the kinetics are different because of the underlying etiologies. METHODS: After quantitative (123)I-MIBG imaging, 76 ischemic and 56 idiopathic cardiomyopathy patients were prospectively followed up for 54 mo. In addition to conventional parameters, cardiac (123)I-MIBG activity was quantified as a heart-to-mediastinum ratio (H/M) for early and late images and the washout kinetics were calculated using tomographic imaging. The data were compared with those obtained from 16 healthy volunteers. RESULTS: During follow-up, 29 deaths from heart failure, 11 sudden cardiac deaths, 2 deaths from arrhythmia, and 5 deaths from acute myocardial infarction were documented. Multivariate discriminant analysis using the Cox proportional hazards model showed that, in comparison with other variables, late H/M was the most powerful independent predictor of a lethal clinical outcome in ischemic (Wald chi(2) = 18.6502; P = 0.0000) and idiopathic (Wald chi(2) = 5.3394; P = 0.0208) groups. When patients with left ventricular ejection fraction (LVEF) < 40% were considered, late H/M had the greatest statistical power in both groups. Kaplan-Meier analysis showed late H/M to have an identical threshold (1.82) for both groups for identifying patients at risk of cardiac death. Likewise, when analysis was restricted to patients with an LVEF < 40%, the upper cutoff value of late H/M was 1.50 (P = 0.0358; log rank = 4.41) for ischemic patients and 2.02 (P = 0.0050; log rank = 7.86) for idiopathic patients. For patients with an LVEF < 40% and a late H/M less than the identified threshold of late H/M, the annual rate of cardiac death was greatest, 18.2%/y for the ischemic group and 11.9%/y for the idiopathic group. CONCLUSION: Cardiac (123)I-MIBG activity has the most powerful independent long-term prognostic value for both ischemic cardiomyopathy patients and idiopathic cardiomyopathy patients, indicating that both disease processes have common pathophysiologic and prognostic implications of impaired cardiac sympathetic innervation. Although combined testing of cardiac function and (123)I-MIBG activity is most likely to identify patients at increased risk of cardiac death, the underlying etiology of cardiac dysfunction may affect the threshold of (123)I-MIBG activity for the differentiation of high-risk patients.     

Diabetic cardiac autonomic dysfunction: Parasympathetic versus sympathetic

Background  

Diabetic cardiac autonomic dysfunction often causes lethal arrhythmia and sudden cardiac death.¹²³I-Metaiodobenzylguanidine (MIBG) can evaluate cardiac sympathetic dysfunction, and analysis of heart rate variability (HRV) can reflect cardiac parasympathetic activity. We examined whether cardiac parasympathetic dysfunction assessed by HRV may correlate with sympathetic dysfunction assessed by MIBG in diabetic patients.     

Sudden cardiac death in patients with congestive heart failure: Toward a unified rational treatment approach

Summary  The problem of SCD in patients with CHF is complex and multifactorial; its solution seems best addressed with a multidisciplinary approach in which heart failure and electrophysiologic factors are continuously evaluated (Table 2). This type of collaboration with optimal CHF therapy and avoidance of antiarrhythmic drugs (except for amiodarone when necessary) has reduced the total and SCD 1-year mortality in status 2 patients awaiting heart transplantation to approximately 15% and 10%, respectively, in several recent series.^52,53 The challenges remaining for nuclear cardiology include the following. (1) Can better techniques be identified to risk stratify patients, particularly those with nonischemic cardiomyopathy? What is the incremental value of measuring variables such as infarct size, EF (left and right ventricular), and ventricular volumes in predicting response to ICD or antiarrhythmic drug therapy⁵⁴? Identification of high-risk groups may justify aggressive treatment with amiodarone or ICD therapy even if these strategies are not helpful in the general CHF population.⁵⁵ (2) Can nuclear imaging techniques be used to identify all patients who would benefit from coronary revascularization? Does the benefit of CABG extend to patients who do not have an increase in EF after surgery either by reducing SCD risk or preventing progressive LV dilation? The optimal care of an extremely needy and growing proportion of patients awaits the answers to these questions. Future trials of therapy for sudden death in patients with CHF will require continued active participation of the nuclear cardiology community.     

I-123 MIBG imaging and heart rate variability analysis to predict the need for an implantable cardioverter defibrillator

BACKGROUND: Iodine 123 metaiodobenzylguanidine (MIBG) imaging and heart rate variability (HRV) analysis were compared in patients with an implantable cardioverter defibrillator (ICD) who did and did not receive defibrillator discharges. Although the ICD has been shown to abort potentially fatal ventricular arrhythmias, identification of patients who most benefit from this device remains difficult. As the autonomic nervous system has been implicated in the genesis of these arrhythmias, we undertook a pilot study to evaluate local myocardial sympathetic innervation with the use of I-123 MIBG myocardial imaging, as well as central autonomic tone with the use of HRV, in patients with implantable defibrillators. Test results were correlated with the occurrence of ICD discharges. METHODS AND RESULTS: Seventeen patients with previously implanted defibrillators were studied. Of these, 10 had at least 1 appropriate device discharge for ventricular tachyarrhythmias, whereas 7 had no discharge. Patients with a discharge had a significantly lower I-123 MIBG heart-mediastinal tracer uptake ratio, higher I-123 MIBG defect scores, more extensive sympathetic denervation, and significantly reduced values for several HRV parameters, particularly those in the frequency domain. When combined, the I-123 MIBG heart-mediastinal ratio and HRV 5-minute low-frequency variables were highly predictive of defibrillator discharges. All patients with a heart-mediastinal ratio lower than 1.54 and 5-minute low frequency lower than 443 ms(2) had an ICD discharge (4/4), whereas no patient with an uptake ratio greater than 1.54 and 5-minute low frequency greater than 443 ms(2) did (0/3, P =.03). CONCLUSIONS: Cardiac autonomic assessment using a combination of myocardial scintigraphic and neurophysiologic techniques may help select patients who would most benefit from an implantable defibrillator by identifying those at increased risk for potentially fatal arrhythmias.     

埋藏式心脏复律除颤器预防心源性猝死研究进展

【摘要】　随着现代医学的发展，心脏疾患治疗成功率大为提升。然而，由于人口老龄化加速及心脏疾病患者心室重构和心功能持续恶化，心源性猝死（SCD）发生率并未下降，而是呈逐年上升趋势。埋藏式心脏复律除颤器（ICD）是目前预防SCD最确切有效的方法,越来越多临床研究关注ICD植入术，以预防心血管疾病高危人群SCD发生。该文就SCD发病原因、预防及ICD预防SCD研究现状作一综述。     

Cardiac MRI and CT features of inheritable and congenital conditions associated with sudden cardiac death

Cardiac MRI (CMR) and electrocardiogram (ECG)-gated multi-detector computed tomography (MDCT) are increasingly important tools in the identification and assessment of cardiac-related disease processes, including those associated with sudden cardiac death (SCD). While the commonest cause of SCD is coronary artery disease (CAD), in patients under 35 years inheritable cardiomyopathies such as hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy are important aetiologies. CMR in particular offers both accurate delineation of the morphological abnormalities associated with these and other conditions and the possibility for risk stratification for development of ventricular arrhythmias with demonstration of macroscopic scar by delayed enhancement imaging with intravenous gadolinium.     

Life-Threatening Ventricular Arrhythmias: Current Role of Imaging in Diagnosis and Risk Assessment

Sudden cardiac arrest continues to be a major cause of death from cardiovascular disease but our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Left ventricular ejection fraction is inversely related to the risk of sudden death but has a low sensitivity and specificity for the population at risk. Nevertheless, it continues to be the main variable considered in identifying patients most likely to benefit from implantable defibrillators to prevent sudden death. Imaging myocardial sympathetic innervation with PET and SPECT as well as imaging characteristics of myocardial infarcts using gadolinium-enhanced cardiac magnetic resonance are emerging as imaging modalities that may further refine patient selection beyond ejection fraction. This review will primarily focus on employing advanced imaging approaches to identify patients with left ventricular dysfunction that are most likely to develop lethal arrhythmias and benefit from inserting a primary prevention implantable cardiac defibrillator. While not yet tested in prospective studies, we will review risk prediction models incorporating quantitative imaging and biomarkers that have been developed that appear promising to identify those at highest risk of sudden death.     

Relationship between late ventricular potentials and myocardial 123I-metaiodobenzylguanidine scintigraphy in patients with dilated cardiomyopathy with mild to moderate heart failure: results of a prospective study of sudden death events

Purpose

Late ventricular potentials (LPs) are considered to be useful for identifying patients with heart failure at risk of developing ventricular arrhythmias. ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy, which is used to evaluate cardiac sympathetic activity, has demonstrated cardiac sympathetic denervation in patients with malignant ventricular tachyarrhythmias. This study was undertaken to clarify the relationship between LPs and ¹²³I-MIBG scintigraphy findings in patients with dilated cardiomyopathy (DCM).

Methods

A total of 56 patients with DCM were divided into an LP-positive group (n?=?24) and an LP-negative group (n?=?32). During the compensated period, the delayed heart/mediastinum count (H/M) ratio, delayed total defect score (TDS), and washout rate (WR) were determined from ¹²³I-MIBG images and plasma brain natriuretic peptide (BNP) concentrations were measured. Left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and left ventricular ejection fraction (LVEF) were simultaneously determined by echocardiography.

Results

LVEDV, LVESV, LVEF and plasma BNP concentrations were similar in the two groups. However, TDS was significantly higher (35?±?8 vs. 28?±?6, p?p?p?p?p?p?Conclusion The present study demonstrated that the values of cardiac ¹²³I-MIBG scintigraphic parameters were worse in LP-positive DCM patients than in LP-negative DCM patients. Furthermore, in LP-positive DCM patients with a high WR, the incidence of sudden death events was higher than that in other subgroups of DCM patients.