Efficacy of Diagnostic Testing of Suspected Coronary Artery Disease: A Contemporary Review.

Coronary artery disease (CAD) affects over 20 million Americans and its' spectrum of impact leads to an estimated 7 million deaths, as well as the loss of 129 million disability-adjusted life years, worldwide, each year. CAD develops as atherosclerotic plaque forms in the coronary arteries. These plaques can eventually limit blood flow to myocardial tissue resulting in ischemia a risk for acute plaque rupture and acute coronary syndrome. While chest pain may represent a wide array of underlying diseases, given the high morbidity and mortality associated with CAD, an ischemic cardiac etiology must always be considered. Early diagnosis and treatment of CAD can improve patient outcomes through guiding risk factor modification and treatment modalities including medical and invasive approaches. While discovering coronary disease early can allow for treatments which can yield great benefit13, many tests are equivocal and can be associated with additional risk and unnecessary cost. This leaves the question; if there is some concern for stable CAD, who should we test, and which modality should be used? This comprehensive review aims to describe the available CAD testing modalities, detail their risks and benefits, and describe when each should be considered in the evaluation of a patient with suspected CAD. (Central illustration).

The Current State of Coronary Revascularization: Coronary Artery Bypass Graft Surgery Versus Percutaneous Coronary Interventions.

PURPOSE OF REVIEW: The optimal revascularization strategy for coronary artery disease depends on various factors, such as disease complexity, patient characteristics, and preferences. Including a heart team in complex cases is crucial to ensure optimal outcomes. Decision-making between percutaneous coronary intervention and coronary artery bypass grafting must consider each patient's clinical profile and coronary anatomy. While current practice guidelines offer some insight into the optimal revascularization approach for the various phenotypes of coronary artery disease, the evidence to support either strategy continues to evolve and grow. Given the large amount of contemporary data on revascularization, this review aims to comprehensively summarize the literature on coronary artery bypass grafting and percutaneous coronary intervention in patients across the spectrum of coronary artery disease phenotypes. RECENT FINDINGS: Contemporary evidence suggests that for patients with triple vessel disease, coronary artery bypass grafting is preferred over percutaneous coronary intervention due to better long-term outcomes, including lower rates of death, myocardial infarction, and target vessel revascularization. Similarly, for patients with left main coronary artery disease, both percutaneous coronary intervention and coronary artery bypass grafting can be considered, as they have shown similar efficacy in terms of major adverse cardiac events, but there may be a slightly higher risk of death with percutaneous coronary intervention. For proximal left anterior descending artery disease, both percutaneous coronary intervention and coronary artery bypass grafting are viable options, but coronary artery bypass grafting has shown lower rates of repeat revascularization and better relief from angina. The Synergy Between PCI with Taxus and Cardiac Surgery score can help in decision-making by predicting the risk of adverse events and guiding the choice between percutaneous coronary intervention and coronary artery bypass grafting. European and American guidelines both agree with including a heart team that can develop and lay out individualized, optimal treatment options with respect for patient preferences. The debate between coronary artery bypass grafting versus percutaneous coronary intervention in multiple different scenarios will continue to develop as technology and techniques improve for both procedures. Risk factors, pre, peri, and post-procedural complications involved in both revascularization strategies will continue to be mitigated to optimize outcomes for those patients for which coronary artery bypass grafting or percutaneous coronary intervention provide ultimate benefit. Methods to avoid unnecessary revascularization continue to develop as well as percutaneous technology that may allow patients to avoid surgical intervention when possible. With such changes, revascularization guidelines for specific patient populations may change in the coming years, which can serve as a limitation of this time-dated review.

Restenosis rates for drug-eluting stents used in treating small vessel cardiac allograft vasculopathy after orthotopic heart transplantation.

BACKGROUND: Cardiac allograft vasculopathy (CAV) is associated with increased mortality in patients with orthotopic heart transplantation (OHT). In addition to immunosuppression, CAV can be treated with percutaneous coronary intervention (PCI) with drug eluting stents (DES) for focal lesions. There is a paucity of data on the rate of DES restenosis in patients with small vessel CAV. METHODS: This was a retrospective observational study of 101 coronary vessels treated with a DES diameter of 2.5 mm or less (small vessels) in 61 OHT patients compared to 72 coronary vessels treated with a DES diameter of >2.5 mm (large vessels) in 44 OHT patients at a single center between 2004 and 2022. Baseline demographic data, angiographic characteristics, and clinical outcomes were analyzed. RESULTS: At an average of 1.6 years after DES placement, follow-up angiography revealed in-stent restenosis in 36 (39 %) small vessel interventions and 11 (17 %) large vessel interventions (p = 0.003). Long term mortality did not differ between the groups (59 % vs 59 % at a median of 4.7 [IQR 2.4-7.8] years follow up). CONCLUSION: DES restenosis rates are high in small vessel CAV. Additional studies specifically examining PCI in small vessel CAV as well as the potential role for newer treatment strategies for CAV are warranted.

Spontaneous coronary artery dissection outcomes among pregnant vs. non-pregnant women.

AIMS: Spontaneous coronary artery dissection (SCAD) has become increasingly recognized. It accounts for <1-4% of acute coronary syndrome presentations. Overall, however, it makes up over 40% of pregnancy-associated myocardial infarction. Furthermore, pregnancy-associated spontaneous coronary artery dissection (P-SCAD) is described to have a greater degree of clinical manifestations, including left ventricular dysfunction, shock, and left main or multivessel involvement. The findings are disconcerting, though many studies evaluating P-SCAD are based on case series data or are single centre studies. METHODS AND RESULTS: The aim of this study was to evaluate a larger national dataset to evaluate the outcomes of SCAD and specifically P-SCAD in an attempt to better characterize the severity and clinical nature of this condition. To conduct this study, we analysed the National Readmission Database from January 2016 to December 2020. Propensity matching was done using the Greedy 1:1 method. Multivariate logistics and time-to-event Cox regression analysis models were built by including all confounders significantly associated with the outcome on univariable analysis with a cut-off P-value of 0.2. In multivariate regression analysis, P-SCAD patients had a non-propensity matched odds ratio (OR) of 0.21 (0.3-1.54, P = 0.123) of dying and a propensity matched OR of 0.11 (0.02-0.61, P = 0.012) of dying. Thirty-day readmission rate for P-SCAD was 15.8% (n = 93) and for non-pregnant spontaneous coronary artery dissection (NP-SCAD) was 11.2% (n = 2286); non-propensity matched OR for readmission for PSCAD patients was 1.68 (1.24-2.29, P = 0.001) and propensity matched OR was 3.39 (1.93-5.97, P < 0.001). CONCLUSION: Among hospitalized patient, P-SCAD was associated with similar clinical outcomes and reduced incidence of death when compared with NP-SCAD, though had higher rates of 30-day readmission. Larger-scale observational data will be needed to ascertain the true incidence of cardiovascular complications as it relates to P-SCAD.

Acute Myocardial Infarction: Etiologies and Mimickers in Young Patients.

Acute myocardial infarction is an important cause of death worldwide. While it often affects patients of older age, acute myocardial infarction is garnering more attention as a significant cause of morbidity and mortality among young patients (<45 years of age). More specifically, there is a focus on recognizing the unique etiologies for myocardial infarction in these younger patients as nonatherosclerotic etiologies occur more frequently in this population. As such, there is a potential for delayed and inaccurate diagnoses and treatments that can carry serious clinical implications. The understanding of acute myocardial infarction manifestations in young patients is evolving, but there remains a significant need for better strategies to rapidly diagnose, risk stratify, and manage such patients. This comprehensive review explores the various etiologies for acute myocardial infarction in young adults and outlines the approach to efficient diagnosis and management for these unique patient phenotypes.

Integrative Genetic Approach Facilitates Precision Strategies for Acute Myocardial Infarction.

Acute myocardial infarction remains a significant cause of mortality worldwide and its burden continues to grow. Its pathophysiology is known to be complex and multifactorial, with several acquired and inherited risk factors. As advances in technology and medical therapy continue, there is now increasing recognition of the role that genetics play in the development and management of myocardial infarction. The genetic determinants of acute coronary syndrome are still vastly understudied, but the advent of whole-genome scanning and genome-wide association studies has significantly expanded the current understanding of genetics and simultaneously fostered hope that genetic profiling and gene-guided treatments could substantially impact clinical outcomes. The identification of genes associated with acute myocardial infarction can help in the development of personalized medicine, risk stratification, and improved therapeutic strategies. In this context, several genes have been studied, and their potential involvement in increasing the risk for acute myocardial infarction is being investigated. As such, this article provides a review of some of the genes potentially related to an increased risk for acute myocardial infarction as well as the latest updates in gene-guided risk stratification and treatment strategies.

Aortic Stenosis Phenotypes and Precision Transcatheter Aortic Valve Implantation.

Patients with a clinical indication for aortic valve replacement can either undergo surgical aortic valve replacement (SAVR) or Transcatheter Aortic Valve Implantation (TAVI). There are many different factors that go into determining which type of replacement to undergo, including age, life expectancy, comorbidities, frailty, and patient preference. While both options offer significant benefits to patients in terms of clinical outcomes and quality of life, there is growing interest in expanding the indications for TAVI due to its minimally invasive approach. However, it is worth noting that there are several discrepancies in TAVI outcomes in regards to various endpoints, including death, stroke, and major cardiovascular events. It is unclear why these discrepancies exist, but potential explanations include the diversity of etiologies for aortic stenosis, complex patient comorbidities, and ongoing advancements in both medical therapies and devices. Of these possibilities, we propose that phenotypic variation of aortic stenosis has the most significant impact on post-TAVI clinical outcomes. Such variability in phenotypes is often due to a complex interplay between underlying comorbidities and environmental and inherent patient risk factors. However, there is growing evidence to suggest that patient genetics may also play a role in aortic stenosis pathology. As such, we propose that the selection and management of TAVI patients should emphasize a precision medicine approach.

Detection of atrial fibrillation in real world setting in patients with cryptogenic stroke and an implantable loop recorder.

INTRODUCTION: Implantable loop recorders (ILR) are used to screen for atrial fibrillation (AF) in patients with cryptogenic stroke (CS). However, there is limited real-world data regarding the long-term rate of AF detection using ILR and management consequences in patients with CS. The objective is to assess the rate of AF detection in patients with CS in a real-world study over 36 months of follow-up and its consequences on stroke prevention. METHODS: This retrospective study included patients with an ILR placed for CS at Baylor College of Medicine and Baylor St. Luke's Medical Center between January 2014 and July 2021. The primary outcome was AF detection in patients with ILR. The secondary outcome was the rate of subsequent strokes after ILR placement in patients with or without diagnosed AF. The AF detection rate in our cohort was compared to the rate in CRYSTAL-AF Trial at 36-month follow-up. The impact of AF detection on clinical management was examined. RESULTS: We identified 225 patients. 51.1% were women and 38.2% African American. Among 85 patients with ILR labeled AF, 43 patients had true AF, and 42 had incorrectly labeled AF (48.3% false positive). The estimated AF detection rate at 36 months follow-up was 28.6% (95% CI, 26.6%-30.6%). 58.1% of patients with AF were initiated on oral anticoagulation, 80.0% of whom were started on a direct oral anticoagulant. 13.8% of patients had recurrent strokes after ILR implantation; 4 of whom were diagnosed with AF. CONCLUSION: Compared to CRYSTAL-AF, the AF detection rate in our cohort is similar, but this cohort includes a higher proportion of female and African American patients. Most patients with recurrent strokes after ILR implant did not have AF during 36 months of monitoring.

Readmission in patients undergoing percutaneous patent foramen ovale closure in the United States.

Current estimates suggest that a patent foramen ovale (PFO) may exist in up to 25% of the general population and is a potential risk factor for embolic, ischemic stroke. PFO closure complications include bleeding, need for procedure-related surgical intervention, pulmonary emboli, device malpositioning, new onset atrial arrhythmias, and transient atrioventricular block. Rates of PFO closure complications at a national level in the Unites States remain unknown. To address this, we performed a contemporary nationwide study using the 2016 and 2017 Nationwide Readmissions Database (NRD) to identify patterns of readmissions after percutaneous PFO closure. In conclusion, our study showed that following PFO closure, the most common complications were atrial fibrillation/atrial flutter followed by acute heart failure syndrome, supraventricular tachycardia and acute myocardial infarction.

Association of pessimism with cardiovascular events and all-cause mortality.

Poor psychological health is associated with Takotsubo cardiomyopathy, cardiac syndrome X, coronary microcirculatory dysfunction, peripheral artery disease, or spontaneous coronary artery dissection. Data regarding pessimism, cardiovascular disease (CVD) events and mortality and all-cause mortality remained inconclusive. This systematic review and meta-analysis aim to provide an overview of the association between pessimism, CVD outcomes and mortality. A systematic search of electronic databases was conducted from inception through July 2022 for studies evaluating pessimism and adverse outcomes. A total of 17 studies published between 1966 and July 2022 met our inclusion criteria, for a total of 232,533 individuals. Pooled hazard ratios were calculated in random-effects meta-analyses. Based on pooled analysis of adjusted HRs, pessimism was associated with adjusted HR of 1.13 (95% CI 1.07-1.19) for all-cause mortality with minimal heterogeneity (I2 = 28.5%). Based on pooled analysis of adjusted HRs, pessimism was associated with adjusted HR of 1.30 (95% CI 0.43-3.95) for CHD mortality, adjusted HR of 1.41 (95% CI 1.05-1.91) for CVD mortality, and adjusted HR of 1.43 (95% CI 0.64-3.16) for stroke. In conclusion, pessimism seems to be significantly associated with a higher risk for and poorer outcomes from CVD events than optimistic styles. There are genetic and other bases for these life approaches, but behavioral, cognitive and meditative interventions can modify patients' level of pessimism, hopefully leading to better medical outcomes. Testing this theory would yield highly useful and practical data for clinical care.

Innovations in ventricular tachycardia ablation.

Catheter ablation of ventricular arrhythmias (VAs) has evolved significantly over the past decade and is currently a well-established therapeutic option. Technological advances and improved understanding of VA mechanisms have led to tremendous innovations in VA ablation. The purpose of this review article is to provide an overview of current innovations in VA ablation. Mapping techniques, such as ultra-high density mapping, isochronal late activation mapping, and ripple mapping, have provided improved arrhythmogenic substrate delineation and potential procedural success while limiting duration of ablation procedure and potential hemodynamic compromise. Besides, more advanced mapping and ablation techniques such as epicardial and intramyocardial ablation approaches have allowed operators to more precisely target arrhythmogenic substrate. Moreover, advances in alternate energy sources, such as electroporation, as well as stereotactic radiation therapy have been proposed to be effective and safe. New catheters, such as the lattice and the saline-enhanced radiofrequency catheters, have been designed to provide deeper and more durable tissue ablation lesions compared to conventional catheters. Contact force optimization and baseline impedance modulation are important tools to optimize VT radiofrequency ablation and improve procedural success. Furthermore, advances in cardiac imaging, specifically cardiac MRI, have great potential in identifying arrhythmogenic substrate and evaluating ablation success. Overall, VA ablation has undergone significant advances over the past years. Innovations in VA mapping techniques, alternate energy source, new catheters, and utilization of cardiac imaging have great potential to improve overall procedural safety, hemodynamic stability, and procedural success.

Outcomes by Class of Anticoagulant Use for Nonvalvular Atrial Fibrillation in Patients With Active Cancer.

Background: The choice of anticoagulant agent for patients with nonvalvular atrial fibrillation (NVAF) in the setting of active cancer has not been well studied. Objectives: The aim of this study was to compare the rates of cerebrovascular accident (CVA), gastrointestinal bleeding (GIB), and intracranial hemorrhage (ICH) in patients treated with direct oral anticoagulant agents (DOACs) compared with warfarin for NVAF in patients with active cancer. Methods: This was a retrospective electronic medical record review of eligible patients treated at a cancer hospital. The outcome events were CVA; GIB; ICH; the composite of GIB, CVA, or ICH; and overall mortality. Propensity score matching (1:1) was conducted to select comparable patients receiving warfarin vs DOACs. Fine-Gray models were fitted for each outcome event. Results: The study cohort included 1,133 patients (mean age 72 ± 8.8 years, 42% women), of whom 74% received DOACs (57% received apixaban). After propensity score matching, 195 patients were included in each anticoagulant agent group. When comparing warfarin with DOACs, there were similar risks for CVA (subdistribution HR: 0.738; 95% CI: 0.334-1.629); ICH (subdistribution HR: 0.295; 95% CI: 0.032-2.709); GIB (subdistribution HR: 1.819; 95% CI: 0.774-4.277); and the composite of GIB, CVA, or ICH (subdistribution HR: 1.151; 95% CI: 0.645-2.054). Conclusions: Patients with active cancer had similar risks for CVA, ICH, and GIB when treated with DOACs compared with warfarin for NVAF.

Antacid Therapy in Coronary Artery Disease and Heart Failure: Proton Pump Inhibitors vs. H2 Receptor Blockers.

PURPOSE: Acid suppressive therapy using histamine H2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) can be utilized for the prevention of gastrointestinal bleeding (GIB) among patients with cardiovascular disease receiving dual antiplatelet therapy (DAPT). However, emerging data suggests underlying associations between PPI or H2RA use and cardiovascular disease incidence, progression, and mortality. This review explores the history of acid suppressive therapies and their use in cardiovascular disease patients and the growing evidence in support of H2RA use. RECENT FINDINGS: PPIs were originally championed as better than H2RAs for preventing GIB events in cardiovascular disease patients on DAPT therapy, but there is evidence to suggest that drug-drug interactions between clopidogrel and PPIs may translate to worse cardiovascular outcomes. Studies demonstrating PPI superiority in the setting of DAPT were also limited due to small sample sizes and high levels of bias. Consequently, there is renewed interest in H2RAs for patients on DAPT with some data demonstrating similar or improved clinical outcomes over PPI therapy. Additionally, studies have discovered a possible role for H2RAs in the management of heart failure (HF) incidence, symptoms, and mortality. Studies comparing H2RAs and PPIs in patients on DAPT have demonstrated mixed results for cardiovascular and GIB outcomes, with several studies being underpowered and limited by biases. Recent clinical and pre-clinical studies now support the noninferiority of H2RAs for major outcomes and even utility in HF. These findings suggest that H2RAs may warrant reconsideration as an acid suppressive therapy over PPIs for patients on DAPT or with HF.

Alcohol Consumption and Cardiovascular Health.

BACKGROUND: Studies evaluating alcohol consumption and cardiovascular diseases have shown inconsistent results. METHODS: We performed a systematic review of peer-reviewed publications from an extensive query of Ovid MEDLINE, Ovid Embase, Ovid Cochrane Database of Systematic Reviews, Scopus, and Web of Science from database inception to March 2022 for all studies that reported the association between alcohol consumption in terms of quantity (daily or weekly amounts) and type of beverage (wine, beer or spirit) and cardiovascular disease events. RESULTS: The study population included a total of 1,579,435 individuals based on 56 cohorts from several countries. We found that moderate wine consumption defined as 1-4 drinks per week was associated with a reduction in risk for cardiovascular mortality when compared with beer or spirits. However, higher risk for cardiovascular disease mortality was typically seen with heavier daily or weekly alcohol consumption across all types of beverages. CONCLUSIONS: It is possible that the observational studies may overestimate the benefits of alcohol for cardiovascular disease outcomes. Although moderate wine consumption is probably associated with low cardiovascular disease events, there are many confounding factors, in particular, lifestyle, genetic, and socioeconomic associations with wine drinking, which likely explain much of the association with wine and reduced cardiovascular disease events. Further prospective study of alcohol and all-cause mortality, including cancer, is needed.

Innovations in Cardiac Implantable Electronic Devices.

Cardiac implantable electronic devices (CIEDs) are essential for the management of a variety of cardiac conditions, including tachyarrhythmias, bradyarrhythmias, and medically refractory heart failure (HF). Recent advancements in CIED technology have led to innovative solutions that overcome shortcomings associated with traditional devices or address unmet needs. Leadless pacemakers, subcutaneous implantable cardioverter defibrillators (ICDs), and extravascular ICDs eliminate lead-related complications common with conventional pacemakers or ICDs. Conduction system pacing (His bundle pacing and left bundle branch pacing) is a more physiologic method of pacing and avoids the deleterious consequences associated with long-term right ventricular pacing. For HF-related devices, cardiac contractility modulation is an emerging therapy that bridges a gap for many patients ineligible for cardiac resynchronization therapy and has been shown to improve HF symptoms and decrease hospitalizations and mortality in select patients. Implantable pulmonary artery pressure monitors help guide HF management and reduce hospitalizations. Lastly, new phrenic nerve stimulating devices are being utilized to treat central sleep apnea, a common comorbidity associated with HF. While further long-term studies are still underway for many of these new technologies, it is anticipated that these devices will become indispensable therapeutics in the expanding cardiovascular armamentarium.

Cilostazol: a Review of Basic Mechanisms and Clinical Uses.

Primarily used in the treatment of intermittent claudication, cilostazol is a 2-oxyquinolone derivative that works through the inhibition of phosphodiesterase III and related increases in cyclic adenosine monophosphate (cAMP) levels. However, cilostazol has been implicated in a number of other basic pathways including the inhibition of adenosine reuptake, the inhibition of multidrug resistance protein 4, among others. It has been observed to exhibit antiplatelet, antiproliferative, vasodilatory, and ischemic-reperfusion protective properties. As such, cilostazol has been investigated for clinical use in a variety of settings including intermittent claudication, as an adjunctive for reduction of restenosis after coronary and peripheral endovascular interventions, and in the prevention of secondary stroke, although its widespread implementation for indications other than intermittent claudication has been limited by relatively modest effect sizes and lack of studies in western populations. In this review, we highlight the pleiotropic effects of cilostazol and the evidence for its clinical use.

Association of PCSK9 Variants With the Risk of Atherosclerotic Cardiovascular Disease and Variable Responses to PCSK9 Inhibitor Therapy.

Genetic polymorphisms or variations, randomly distributed in a population, may cause drug-gene response variations. Investigation into these polymorphisms may identify novel mechanisms contributing to a specific disease process. Such investigation necessitates the use of Mendelian randomization, an analytical method that uses genetic variants as instrumental variables for modifiable risk factors that affect population health.1 In the past decade, advances in our understanding of genetic polymorphisms have enabled the identification of genetic variants in candidate genes that impact low-density lipoprotein cholesterol (LDL-C) regulating pathways and cardiovascular disease (CVD) outcomes. A specific candidate gene of interest is that of the LDL receptor degrading protein, PCSK9. In fact, loss-of-function genetic variants for the PCSK9 gene are what first highlighted this pathway as a candidate for pharmacologic inhibition. PCSK9 inhibitors (PCSK9i) are a class of cholesterol-lowering medications that provide significant reductions in LDL by inhibiting the degradation of LDL receptors (LDLR). These inhibitors have also been found to reduce production and enhance clearance of lipoprotein A (Lp[a]), an LDL-like particle currently under study as a separate risk factor for atherosclerotic CVD. Here, we discuss the promise of personalized medicine in developing a more efficacious and individualized pharmacogenomics-based approach for the use of PCSK9i that considers genetic variation and targets different patient populations. This review explores the pharmacogenomics of PCSK9i in the context of PCSK9 allele variants related to drug-metabolizing enzymes and responses since more studies are demonstrating that some patients are hyporesponsive or non-responsive to PCSK9i.2 In summary, the pharmacogenomics of PCSK9 are a promising therapeutic target and genetic information from prospective randomized clinical trials is warranted to gain a full understanding of the efficacy and cost-effectiveness of such allele and/or gene-guided PCSK9i therapy.

Diagnosis of Occlusion Myocardial Infarction in Patients with Left Bundle Branch Block and Paced Rhythms.

PURPOSE OF REVIEW: A number of criteria have been developed to aid with the diagnosis of occlusion myocardial infarction (OMI) in patients with left bundle branch block (LBBB) and ventricular paced rhythms (VPR). The current guidelines do not provide clear preference for any specific ECG criteria in LBBB and paced rhythm patients. RECENT FINDINGS: This review delineates the difficulties of electrocardiographic diagnosis of OMI in both LBBB and VPR patients. We describe the original Sgarbossa and the newer criteria and their diagnostic performances. We highlight the expected changes of newer pacing modalities and how they may interfere with the electrocardiographic diagnosis of OMI. We recommend utilizing the Cai et al. algorithm, which combines clinical assessment with the Smith Modified Sgarbossa ECG criteria, for both LBBB and right ventricular pacing patients with suspected OMI. There is limited data concerning ECG changes of OMI in patients with the newer pacing modalities, such as biventricular, His-bundle, or left bundle branch pacing.

N-alkoxyheterocycles as irreversible photooxidants.

Irreversible photooxidation based on N-O bond fragmentation is demonstrated for N-methoxyheterocycles in both the singlet and triplet excited state manifolds. The energetic requirements for bond fragmentation are studied in detail. Bond fragmentation in the excited singlet manifold is possible for ππ* singlet states with energies significantly larger than the N-O bond dissociation energy of ca 55 kcal mol(-1). For the nπ* triplet states, N-O bond fragmentation does not occur in the excited state for orbital overlap and energetic reasons. Irreversible photooxidation occurs in the singlet states by bond fragmentation followed by electron transfer. Irreversible photooxidation occurs in the triplet states via bimolecular electron transfer to the donor followed by bond fragmentation. Using these two sensitization schemes, donors can be irreversibly oxidized with oxidation potentials ranging from ca 1.6-2.2 V vs SCE. The corresponding N-ethylheterocycles are characterized as conventional reversible photooxidants in their triplet states. The utility of these sensitizers is demonstrated by irreversibly generating the guanosine radical cation in buffered aqueous solution.