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A  good collection of resources dedicated to cardiology

http://www.touchcardiology.com/articles/primordial-prevention-cardiovascular-disease-the-role-blood-pressure

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  1. Do 64slice MDCT  in all patients who has  a coronary event and follow it up with catheter based CAG.
  2. Use liberally the new biochemical marker ,  serum  B-naturetic peptide (BNP) to diagnose cardiac failure in lieu of basal auscultation.
  3. Advice  cardiac resynchronisation therapy in all patients  who are in class 4 cardiac failure with a wide qrs complex .
  4. As it is may be considered a  crime to administer empirical  heparin, do ventilation perfusion scan in all cases with suspected pulmonary embolism.
  5. Do serial CPK MB and troponin levels in all patients with well  established  STEMI .
  6. Open up all occluded coronary arteries irrespective  of symptoms and muscle viability.
  7. Consider  ablation of pulmonary veins as an  initial strategy in  patients with recurrent idiopathic AF. If it is not feasible  atleast occlude their left atrial appendage with watch man  device.
  8. Never tell  your patients   the  truths  about the  diet , exercise &  lifestyle modification (That can  cure most of the early hypertension) . Instead encourage the  use of  newest ARBs  or even  try direct renin antoagonists   to treat all those patients in  stage 1 hypertension.
  9. Avoid regular heparin in acute coronary syndromes   as  it  is a disgrace to use it  in today’s world. Replace all prescription of heparin with  enoxaparine  or  still better ,  fondaparinux  whenever  possible.
  10. Finally never discharge  a  heftily  insured patient   until  he completes all the  cardiology investigations  that are available in your hospital  .

Coming soon :  10 more ways to  increase cost of cardiology care . . .beyond common man’s reach

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atropine leafsAtropine ,  the extract from the  Belladona  plant  is an important cardiovascular  drug. It’s  presence is vital  in every crash carts .  This  unassuming molecule  probably has   saved more cardiac lifes than any other drug . It provides immediate  remedy for many of the bradycardias .It  works like a magic.  The physician buys  time with this molecule  and  proceed  on to resuscitate or  plan other interventional  procedures. It is most powerful antiarrhytmic agent known .It is an irony , many of  the standard cardiac texts do not even mention this while discussing anti arrhythmic agents .

In  this  era of  hyped  cardiac  care   , the  sartans ,  2b3a inhitors   , the fondaparinux’s  making merry !  we  have no spare time  to realise  ,   more  cardiac  deaths  have been prevented by atropine  than  all these   drugs    put together.  It is still working like a bull  across the coronary care units and cath lab world over. While  many mediocre  drugs  enjoy a  big  bash  time for  possibly  saving   few occasional  lives   , the atropine  like drugs never get the due recognition among cardiac literature for the simple reason ,  it being a  cheap  generic drug.This drug is available  for few  rupees , no marketing no advertisements, no celebrations.

Mechanism of action

The  biochemical  mediator :  Acetyl choline

Site of action :     It blocks the M2 (Muscaranic receptors) .

We will confine to the cardiovascular  actions.

  • SA nodal acceleration
  • AV nodal accelerated conduction

Effect on ECG

Sinus tachycardia

Short PR interval

Life saving situations in cath labs  in CCU.

Vagus  nerve richly innervate the heart and blood vessels . Acute coronary syndromes   especially involving the infero posterior territory  raises the vagal tone  , and can  in severe bradycardia and hypotension.  In cath labs , as we  manipulate  cardiac  structures with wires and  catheters  there is always  a potential to elicit the vascular reflex .It can occur  any where between the  access point , femoral or radial  artery to coronary arteries .

Further ,  whenever the  pain  intensity is more , the  central pain integrating  centre in  brain stem  and thalamus has a spill over effect into the vagal nucleus .

What happens if a vaso vagal reaction is left untreated ?

We have often  made  the term “vaso vagal  reaction” appear as an  innocuous  entity. The main reason for this perception is   due to the common occurrence of  “vaso vagal  syncopewhich  is largely a benign entity in the general population .This fact  has sensitised our brains . One should distinctly realise the vaso vagal syncope that occurs in  healthy people standing  in erect posture ,  from  vagal reactions that  occurs in  lying patient with a diseased heart  in a  cath  lab  or CCU.In the classical vaso vagal syncope , assuming the recumbent posture is the treatment and it  counters the hemodyanmic imbalance .No drug is required here. So the common vagal syncope can never be compared with potentially dangerous  vagal reflex that occur in CCUs and cath labs. If not recognised earlier and  immediately countered  it can lead on to asystole and death .Many of  the delayed deaths post PCI during sheath removal or an episode of vomiting are directly related to this.

atropine

Atropine is the Savior here . Can you imagine a  world without atropine .

The other reason we had always considered vaso vagal   reactions lightly is that the poor atropine is always available  in the side selfs and it acts   rapidly  and promptly with almost  100 % success  reversing the vagal action  in less than  60 seconds .

How often we here  this  “Oh it’s a brady . . . push  2cc atropine . . .  given sir, the rate has picked up . . .”

If only atropine has a failure rate of say  50%    we  would have  realised the full impact of   vaso vagal shocks (See … how we struggle with No reflow   with no effective drug available !)

Is there any other alternative  treatment  for vaso vagal shock other  than atropine ?

No.   (I guess so . . .Readers may correct me )

Other uses of atropine in cardiac practice

  • During stress testing along with dobutamine  to  increase the heart rate.
  • It can be used to differentiate AV blocks the two types of 2nd degree AV block. The mobitz type 2 worsens while type one accelerates.

Non cardiac uses.

Ophthalmology, pre anesthetic medication, bronchial asthma, various poisoning.

What is the future for this molecule ?

Remain bright .  But only very  few companies make this molecule.  It is a drug that can not  fill the cash boxes but  it is a drug to keep the human heart running at times of crises  . The only  threat to this drug  is  the  possibility of it being replaced with a  modified patented  version of this great  molecule  !

Final message

The evolution of medicine is based on strong foundations  put upon by clinical acumen   by great medical men of  past generation. Atropine was developed by such people   and it has withstood the test of time. This drug  probably  has saved ( and  continue to  save)  many  lives  than any  other drug  in cardiology . It should be recalled ,  another great cardiac drug   called digoxin  has almost succumbed to modern medical  forces  .Let us  keep developing   new molecules  ,  we shall also pay  tributes  to some of   the  unassuming drugs in cardiology .

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micro circulation shockHuman circulatory system consists  of  the heart , the arterial  and the venous  systems . Together they constitute the  three important limbs of circulatory system namely , the  pumping, delivering and retrieval systems .In physiological conditions approximately 6 liters of  blood  has to traverse  the entire   circuit every minute . The  purpose of the  circulatory system is not simply circulating the blood within the body,  but  it has to perfuse different vital organs like brain, kidney, liver . Of course ,   the heart has to self perfuse the coronaries  by it’s own contraction.The organ perfusion is determined by local and systemic  regulatory mechanism. A gamut of intrinsic and extrinsic neuro humoral modulators take up this job. A functionally intact autonomic nervous system is an absolute necessity to maintain tissue perfusion.  The perfusion pressure is highly variable in different organs and different cells. Similarly the ability to with stand ischemia and hypoxia also varies. Shock  is a general term used to imply ,  circulation is seriously compromised.Here we will confine our self  to the intricacies of peripheral circulatory shock

Traditionally shock is  classified as

  1. Cardiogenic shock
  2. Hypovolemic shock
  3. Vasodilatory /Redistributive/Septic /Warm shock (Can be called  as  arterial shock )

The hemodynamics of the first two are straight forward and easily understood. In  cardiogenic shock , the pumping action of heart is primarily affected .In hypovolemic shock  there is no  structural defect in any of the   circulatory limbs but there is  a loading defect due to low blood  volume as in hemorhagic shock .

The term vasodilatory shock or redistributive shock is most poorly understood and most difficult to treat.

The  concept is further confounded as  combinations of   above three mechanism in a same a pateint can occur . ( More commoner than we believe !) . An example could be a septic patient  with an  internal bleed and myocardial  depression either due to preexisting LV dysfunction or circulating toxins.

Since  we have always perceived heart as  the  sole  vital  component of circulatory   system , our understanding of the role of the vascular tree which is primarily responsible for delivering the blood is largely undermined and neglected. We are always happy if the EF %  is normal.

Classical features of  circulatory failure ?

The cardiac contraction is good.This is documented by normally contracting LV by echocardiography. The pulmonary capillary wedge pressure is normal (<12mmhg).Still the patient is in  hypotension with  evidence for vital organ under perfusion like oliguria and reduced mentation.

What is vascular tone ? What sustains  the flow of blood into the tissues  ?

The entire  vascular tree could form a   few 100 kilometer length.(Capillary /arterioles /venules included). While , it is easy to  percieve heart as  a dynamic pumping organ ,  it is a less recognised fact the entire vascular tree is also  pulsating  to every beat. That is the rhythm of life. What makes the vascular tree to pulsate ? Apart from  contraction of the heart  , there is an  intrinsic tone for the large , small arteries and the arterioles and veins  .This tone is vital for pushing the bllood into various organs and return into venous circulation and subsequently back into the heart.

microcirculation shock cardiogenic septic

The  millions of perivascular cuffings and the artreriolar smooth muscles  can be considered as  small micro pumping stations situated along side every cell.

It is very important to emphasize here,   if  tone in these microcirculation is less than optimal , the patient’s circulatory  system can never complete the desired circuit  even if the heart has 75% EF . This exactly is happening in circulatory shock . The vascular tree fails to accept and return the pumped blood  in timely fashion.

What controls this tone ?

It is chiefly under the control of autonomic nervous system.The endogenous vasoconstrictors , the adrenergic nervous system, the endothelins , the angoitensins constrict the vascular smmoth muscles while endothelial relaxing factors ,( EDRF -nitric oxide relaxes it ). There is a delicate balance between these forces.

A cardiovascular health of a person is not simply having a healthy heart , he has to have a healthy vascular system with intact biological activity.The fact that , not every one with sepsis react with poor vascular tone indicate inherent capacity to neutralise toxic vasodilatory neuro transmitters.

Is there a invisible parameter called vascular ejection fraction  in circulatory  system?

Yes. It must be . We rarely discuss it . The vascular tree has an important role for pumping the blood into the tissues.  It needs micro manometers to assess the systolic and diastolic dimensions of small arteries and arterioles . But  what  we know is ,  it is grossly impaired in circulatory failure.The vessels especially the arteriolar smooth muscles which determine the perfusion pressure of cells go into state of permanent relaxation. The vascular smooth muscles lose control from autonomic innervation and become flabby. It is the   DCM equivalent for blood vessels. The arterioles no longer regulate blood flow and fluids get sequestrated in various viscera,( often called thrid spaces) and organ dysfucntion sets in. The resultant hypoxia aggarvates the tissue stagnation by producing still unnamed vasodialtory mediators.

What are the pharmocological approches to increase the vascular tone of a failing vascular tree ?

It is a very difficult problem even in this modern era of vascular medcine. Once set in ,  these patients invariably go downhill .The primary underlying problem  ,  often sepsis  need to be corrected. Usually these  patients need multi organ support.Vasoconstrictors like epinephrine,nor epinephrine , dopamine  can sustain vasoconstriction temporarily . As we know the vascualr smooth msucles can not be kept on this assited contrection mode for long.It is bound to fail .Patients native autonomic function has to recover fast to wean of this support.

What is normal circualtorty time .How is it altered in circualtory failure  ?

The normal circualtory time is 15-20 seconds.It is many times prolonged in circualtory failure inspite of the cardiac contraction being normal

What is effective circulatory volume ?

The body fluid compartment is divided into ICF,ECF & interstitial  spaces.At a given time , the fluid in the extracellular space  can only  take  part  in circulation. A good blood pressure does not always mean a good tissue perusion why ? This is very important to realise as blood pool has to dynamically exchange with intra cellullar compartment. At times of shock the blood can bye- pass the cells through the alternate circuits in the periphery of micro circulation. So what is circulating in the system may not be taking part in tissue perfusion .This is the concept of  effective circulatory volume.This is especially noted in hepatic shocks and in some terminally ill malignancy.

Is there a venous shock syndrome ?

Cardiologists  often show a  step motherly  attitude to venous disorders. In fact many  of the   cardiovascular  specialists   think their   job is  taking care of  heart ( Of course , a little bit of aorta and venacava !) .It is surprising  to know,  there is little  scientific data on determinants  venular and venous tone (Both small and large veins).

The power of venous system should not be under estimated  as it pumps  many litres of blood every minute  defying gravity ! For this to happen it needs a vigorous tone .Where do it get from ?  : The same  autonomic nervous system that controls the heart. Remember , in pathological states there is a  great chance for this to go out of control. So venous shock is a clinically distinct possibility. In fact inappropriate administration of nitrates which reduces the venous tone has resulted in many adverse events in RV shock.

In a patient with circulatory shock , we would  never know  how much is contributed by venous side and how much by arterial side .This is important as in circulatory shock we administer all vital drugs through veins.Now it is thought  systemic venous  dysfunction also contribute to shock state.

Clinical situations of circulatory failure or shock

Bacterial shocks

  • Gram negative sepsis
  • Staphylococcal shock

Viral shocks

Dengue/Swine flu etc

Others*

  • Dissiminated intravascular coagulation
  • ARDShypoxic shock
  • Elderly,Diabetic  autonomic neuropathy
  • Persistent post operative hypotension due to silent autonomic neuropathy.
  • Some cases of Spinal shock
  • Toxins – Scorpion etc(Intense vasoconstrictive shock )
  • Terminal shock in liver failure/Hepato pulmonary   syndrome

* Idiopathic unexplained persistent hypotension , with difficulty to wean off from vasoconstrictive agents is a commonly encountered problem in any intensive care unit.The exact mechanism is not known.When we are not clear about the mechanism  we  generally blame it on the  the autonomic nervous system !

How common is the mixed shock syndrome ?

This is more common than we realise .The classical description of multisystem failure is a direct consequence of this.

Can a cardiogenic shock transform into a peripheral circulatory shock ?

Such a scenario is  possible  .A  resuscitated cardiac arrest may end up with a recovered heart but a loss of vascular tone  possibly due to hypoxic vascular damage. .Many times cardiac patients are kept (Post PCI/CABG ) on large doses of  vasoconstrictors or IABP that can induce  tachyphylaxis. It may result in difficulty in weaning these drugs.

How can circulatory shock result compromised cardiac function ?

The common effect of any shock is  reduced organ perfusion.So even in peripheral shock , the coronary blood flow gets compromised especially if these patients have a silent coronary lesions which are otherwise not significant , becomes sites of hemodynamic hurdles during hypotension.This may result in global contractile dysfunction, or a coronary event.

What is vasoconstrictive shock ?

Epinephrine and nor epinephrine are  very potent  vasoconstrictors .If levels of these becomes excessively high , the blood vessels go in for sustained spastic state that can impair the micro circulation .Some times  this results  in a  good blood pressure in the major vessels but severely compromised tissue perfusion.This particular situation has been reported after scorpion envenomation , and in  rare cases of pheochromocytoma .

Final message

Primary circulatory failure or shock (With largely intact cardiac function without hypovolemia) is a common problem in critically ill.  The entire  macro and micro vascular tree goes for a  stunning reaction and  goes for  a sleep in a  semi dilated  state  . It can  be termed as  Arterial  or Arteriolar   shock. Contrary to  all those hi-tech   mechanical stuff for supporting a failing heart (LV assist, Impalla, Abiomed , ) the available options are very little here  . The response to vasoconstrictive agents are  also unpredictable. Correcting the multi organ failure  and targeting the primary cause  is the only hope.

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 Selected on the basis of ,  impact  on survival , relief of  human suffering index and also innovation

10.Percuateneous interventions

9.  Electrocardiography

8 . Hemodynamics of cardiovascular system

7.Fruesemide

6.Thrombolysis

5.Pacemakers

4.Defibrillation

3.Heparin

2.Prosthetic valves

1.Coronary care units

 

Waiting list

Concept of vascular biology

Statins

RF ablation

Nitric oxide

Total Artifitial heart

Echocardiography

 

Ten least important concepts and  inventions in cardiology

Selected based on duplication of research, futile scientific concepts and   of course impact on survival

10.Low molecular weight heparins

9.Cardiac resynchronisation

8.Rotablator

7.Multi  chamber pacing

6.Newer ARBs

5.C reactive protein

4.Three dimensional echocardiography

3.

Comments welcome  and please contibute

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                                        Angina pectoris , classically occur on exertion and gets relieved on rest .This is called typical chronic stable angina as described by Heberden (CSA ) .  Unstable angina(UA), the term originally described by Noble O Fowler in early 1970s. ( Also being referred as  intermediate coronary syndrome , preinfarction angina etc).The definition for unstable angina has evolved  over the years  and currently  refers to .

 1.All new onset angina of any degree* Some include severe angina only ! New onset angina of very mild degree on exertion could be the onset of the first episode of  stable  angina. 

 2.Rest angina of more than >30 mts not relieved by taking sublingual nitroglycerine.

 3.All Post MI angina

 4.Any angina in patients who have been stented by PCI.

How to recognise a patient  who is shifting from  stable angina to  UA ? 
UA is  to be suspected when  a patient develops. 
5.More frequent episodes than usual
6.Angina occurring at lesser level of exertion than before 
7.Angina radiating to new site ( Example : Chest pain radiating  to jaw rather than to the usual left arm or vice versa)

Why the first episode of angina is given a special status and often considered critica ?

Angina is the  clinical expression of   myocardial ischemia.The course of  the  first  episode of angina , can not be predicted.It could be a the beginning of a chronic disease process, or it could be a progressive coronary occlusion as in unstable angina /NSTMEI , or the onset of even a STEMI.
In contrast a patient with chronic stable angina  has a predictable chest pain , at a particular level of exertion, radiation to same site, same character, and the patient knows for sure the pain  would promptly dissappear  when he takes rest or nitroglycerine  tablets.

What is the underlying pathology in UA ?  

Generally it is very rare for  a stable plaque to produce a  serious episode of unstable angina .It  requires  an unstable plaque* to  precipitate an unstable angina !
Unstable plaque refers to any plaque which is eroded, fissured, ruptured or  hanging  eccentrically ,  with
an active thrombus.

What is the significance of post PCI angina?

It is an irony, any angina following PCI is to be considered unstable as sudden occlusion of stent is quiet common.This is a paradox of sorts as one would wonder in a patient  with CSA who undergoes PCI with stenting  of left anterior descending coronary artery  (LAD)  all his subsequent episodes of angina  will be labelled as UA  even if a stable angina occur in his other coronary artery.And these patients would go for early invasive approach and potentially inappropriate interventions even if they are at low risk !

Is all angina at rest can be termed as unstable angina ?

No, but many times ,  rather most of the times  cardiologist believe all rest angina to be unstable.

What are the situations where stable angina can occur at rest?

An episode of angina during mental stress, or post prandial* state are very common in patients with CSA. This gets relieved after the stress. Some times  patients with CSA during episodes of fever may get angina at rest .These are considered variants of stable angina.
Post prandial angina , may be considered by some as unstable

How often a diagnostic confusion occur between CSA and UA ?

Generally, this issue is rarely addressed in cardiology literature , for the  simple reason it is never considered an  issue at all !
According to Canadian cardiovascular society grade 4 stable angina  is almost similar to unstable angina , as it denotes angina occurs with minimal effort or even at rest. In fact CCSC grade 4 should be termed as UA.

Can ECG be useful to identify stable angina from unstable angina ?

                                    ECG will some times  come to our rescue when one is confused between stable and unstable angina even though resting ST depression can occur in both stable and unstable angina . Statistically , if ST depression is noted during an episode of angina it is more likely to be UA rather than CSA. . Apart  from ECG , Troponin T or I levels may be elevated in some of the patients with unstable angina. Rarely stable angina can also show elevated troponin.

In patients with systemic hypertension and LVH or cardiomyopathy resting ST depression may not indicate UA 

So differentiation between, stable and unstable angina even though appear simple and  straight forward, it requires a diligent appraisal of history , physical examination (Aortic stenosis /HCM  may cause stable angina)  and ECG, enzyme evaluation.

Final message

In any coronary care unit ,  admissions with initial diagnosis of  ACS/UA/NSTEMI , subsequently turn out to be simple stable coronary artery disese . This error happens because the chest pain  or ECG changes  are aggravated by non cardiac factors like a mental stress or a post operative stress  or fever etc.
There could  be another school of thought, that is to err on the side of  safety, and manage all  rest angina as UA  .But the hazards of unwarranted therapy might exceed the risks of leaving these patients alone.
In this context ,there is a need for a new definition for unstable angina .
One ideal version could be . . .
  • Any angina , of any degree  which is caused  mainly by the supply side defect (By a acute thrombotic /disruptive plaque   occluding the  coronary lumen  with a imminent danger of myocardial infarction is to termed as real UA.
  •  All post MI and post PCI angina are unstable angina
  •  Rest angina which occurs due to increased demand situations need not be  labelled  as unstable angina for the simple reason  there is neither an active plaque nor a  fresh thrombus likely  in these patients. They rarely develop  recurrent angina or MI . The mechanism of angina at rest here is most often due to a tachycardia and resultant increase in MVO2 .(myocardial oxygen consumption) .Currently they are called as secondary unstable angina.In fact , anti thrombotic drugs are misused in these situations as they satisfy the criteria of UA/NSTEMI.

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Is it true , once a patient is labelled as a hypertensive he remains  hypertensive life long ? Is it possible to withdraw antihypertensive drugs  permanently ?

  • Systemic  hypertension is the most common clinical entity and it forms the bulk of the physician consultations world over.
  • The anti hypertensive drugs are  one of the most commonly  prescribed medication  by the medical professionals .
  •  It is estimated , the major chunk of  revenue to pharma industry is contributed by antihypertensive  drugs.
  •  SHT , is being maintained  as a  major , global cardiovascular risk factor , by  periodically refixing the target blood pressure  to lower levels  by various committees.
  • The terminology of pre hypertension for blood pressure between 120-140 was hugely controversial    and some societies refused  to accept this entity.

Is there a case for withdrawal of anti hypertensive agents  among our patients ?

Yes , in fact there is a strong case for it.

While on the one hand there is a sustained effort ( By whom !)  to increase the drug usage , very early in the course of hypertension , there is also a silent progress in our knowledge ,  regarding withdrawl of anti hypertensive agents in all those undeserving patients .

It is estimated 42% *of the so called hypertensives especially elderly can be successfully weaned of anti hypertensive drugs with out any adverse effect.( Mark R Nelson BMJ. 2002 October 12; 325(7368): 815.)

What are the situations where we can successfully with draw anti hypertensive drugs?

  • The most common group of patients  are the ones, where  the anti hypertensive drugs are  started prematurely , with out giving an option for non drug life style  approach.These patients and their physicians continue to believe , anti HT drugs are sacred and essential !
  • There is another  major group of patients who have had a temporary  elevation of BP due to a stressful environment.These patients  get drugs permanently for a temporary problem . These patients need  to be reassessed.
  • Some of the elderly  patients,  with the onset of  age  related autonomic dysfunction ,these  drugs are poorly tolerated and  even have  disastrous effects .In this population  it is desirable , to wean off the anti HT drugs  and switched over to life style  medication whenever possible.

Final message

Essential or primary hypertension is not a permanent  disease, in bulk of our population. It reflects the  state of  the  blood pressure on a day to day basis  and is a continuous variable. All patients who have been labelled as hypertensives( Either by us or others) should be constantly reviewed  and considered for withdrawal of the drugs if possible.

* Note this rule does not apply in all secondary hypertensions, during  emergencies, uncontrolled hyper tension with co existing CAD /diabetes /dyslipidemias etc .

Please refer to these forgotten Landmark articles

Does Withdrawl of Anti hypertensive Medication 

Increase the Risk of Cardiovascular Events?

The TONE study

Source: The American Journal of Cardiology, Volume 82, Number 12, 15 December 1998 , pp. 1501-1508(8)

http://www.ncbi.nlm.nih.gov/pubmed/9874055

Conclusion of TONE study

The study shows that antihypertensive medication can be safely withdrawn in older persons without clinical evidence of cardiovascular disease who do not have diastolic pressure > or = 150/90 mm Hg at withdrawal, providing that good BP control can be maintained with nonpharmacologic therapy

 

Some of the references for successful withdrawl of antihypertenive drugs

1.Nelson, M; Reid, C; Krum, H; McNeil, J. A systematic review of predictors of maintenance of normotension after withdrawal of antihypertensive drugs. Am J Hypertens. 2001;14:98–105. [PubMed]
2.
Wing, LMH; Reid, CM; Ryan, P; Beilin, LJ; Brown, MA; Jennings, GLR, et al. Second Australian nationalbloodpressure study (ANBP2): Australian comparative outcome trial of ACE inhibitor- and diuretic-based treatment of hypertension in the elderly. Clin Exp Pharmacol Physiol. 1997;19:779–791.
3.
Lee, J. Odds ratio or relative risk for cross-sectional data. Int J Epidemiol. 1994;723:201–203. [PubMed]
4.
Lin, D; Wei, L. The robust inference for the Cox proportional hazards model. J Am Stat Assoc. 1989;84:1074–1079.
5.
Veterans Administration Cooperative Study Group on Antihypertensive Drugs. Return of elevated blood pressure after withdrawal of antihypertensive drugs. Circulation. 1975;51:1107–1113. [PubMed]
6.
Medical Research Council Working Party on the Management of Hypertension. Course of blood pressure in mild hypertensives after withdrawal of long term antihypertensive treatment. BMJ. 1986;293:988–992. [PubMed]
7.
Alderman, MH; Davis, TK; Gerber, LM; Robb, M. Antihypertensive drug therapy withdrawalin a general population. Arch Intern Med. 1986;146:1309–1311. [PubMed]
8.
Blaufox, MD; Langford, HG; Oberman, A; Hawkins, CM; Wassertheil-Smoller, S; Cutter, GR. Effect of dietary change on the return of hypertension after withdrawal of prolonged antihypertensive therapy (DISH). J Hypertension. 1984;2(suppl 3):179–181.
9.
Mitchell, A; Haynes, RB; Adsett, CA; Bellissimo, A; Wilczynski, N. The likelihood of remaining normotensive following antihypertensive drug withdrawal. J Gen Intern Med. 1989;4:221–225. [PubMed]
10.
Myers, MG; Reeves, RA; Oh, PI; Joyner, CD. Overtreatment of hypertension in the community? Am J Hypertens. 1996;9:419–425. [PubMed]
11.
Stamler, R; Stamler, J; Grimm, R; Gosch, F; Dyer, R; Berman, R, et al. Trial of control of hypertension by nutritional means: three year results. J Hypertens. 1984;2(suppl 3):167–170.
12.
Takata, Y; Yoshizumi, T; Ito, Y; Ueno, M; Tsukashima, A; Iwase, M, et al. Comparison of withdrawing antihypertensivetherapy between diuretics and angiotensinconverting enzyme inhibitors in essential hypertensives. Am Heart J. 1992;124:1574–1580. [PubMed]
13.
Whelton, PK; Appel, LJ; Espeland, MA; Applegate, WB; Ettinger, WH; Kostis, JB, et al. Sodium reduction and weight loss in the treatment of hypertension in older persons: a randomised controlled trial of nonpharmacological interventions in the elderly (TONE). JAMA. 1998;279:839–846. [PubMed]
14.
Heart Outcomes Prevention Evaluation Study Investigators. Effects of an angiotensin-converting-enzyme inhibitor, ramipril, on death from cardiovascular causes, myocardial infarction, and stroke in high-risk patients. N Engl J Med. 2000;342:145–153. [PubMed]
15.
Howes, L; Krum, H. Withdrawing antihypertensive treatment. Curr Therapeutics. 1988;November:15–20.
16.
Fotherby, MD; Harper, GD; Potter, JF. General practitioners’ management of hypertension in elderly patients. BMJ. 1992;305:750–752. [PubMed]
17.
Jennings, GL; Reid, CM; Sudhir, K; Laufer, E; Korner, PI. Factors influencing the success of withdrawal of antihypertensive drug therapy. Blood Press Suppl. 1995;2:99–107. [PubMed]

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